Zerg V.S Teren

Marines and Firebats
The biggest early threat to a Zerg brood when facing a Terran opponent will be the Marine and Firebat. Both of these units will tear through Zergling hordes when either Stimpacked or protected by bunkers. Should the Terran infantry be backed by Medics, the situation becomes even worse. The best early game solution is to outproduce your opponent and use a mixed force of Zerglings and Hydralisks. While Zerglings will not fare very well against Firebats, the Zerglings can distract the Marines while your own Hydralisks take out the Firebats. If the Marines and Firebats are accompanied by Medics, you will need much larger numbers, better upgrades, or a favorable defensive piece of terrain to hold off the Terrans with just Zerglings and Hydralisks. The Subterranean Spines of the Lurker are the first definitive counter the Zerg has against Terran infantry. A few Lurkers at a chokepoint can hold off huge numbers of Marines and Firebats, even if the Lurkers are detected by the Terran.

If your opponent continues to massively produce Marines or Firebats during the later stages of the game, use Ultralisks to mow through the enemy infantry lines. If the Ultralisk's Carapace is fully upgraded, the Marines and Firebats will inflict very little damage. Even a single Ultralisk can destroy entire squads at a time. The fast and long ranged attack of the Guardian will also annihilate Terran infantry in an effective manner. Vultures
Vultures can be a nuisance to a Zerg force with their quick speed and Spider Mines, but their power should not be underestimated. Vultures have the capability to execute quick hit and run raids against your Drones, and the Vulture's attack does excellent damage to the small Zerglings. Fields of Spider Mines also prove fairly nasty to an unsuspecting Zergling attack force. Masses of Hydralisks have little to fear from either the Vultures or Spider Mines, but the speed of the Vulture usually allows the Terran to retreat from any engagement. The best counter to the Vulture is the Mutalisk. Since the Vulture has no anti-air capability, the hover bikes make easy targets for the fast moving Mutalisks. Siege Tanks
Siege Tanks are a rather powerful component of the Terran arsenal. Siege Tanks in Siege Mode protected by Bunkers and Missile Turrets can be annoyingly difficult to uproot. The Zerg Swarm does have quite a few counters available for the power of the Siege Tank. The single best counter to a Siege Tank is the Queen's Spawn Broodling ability. Each use of this ability will instantly destroy a Siege Tank. A group of Queens can quickly clear out an entire Tank blockade. Since the ability is reusable, Queens only need to recharge their energy before being able to wreak havoc against more Siege Tanks. When using Spawn Broodling, be sure to pick the Tanks that are in the middle of a Tank group or right next to a Bunker or Missile Turret. As soon as that Tank is destroyed, any other Tanks within range will open fire on the Broodlings in their midst. The Siege Tank fire will cause splash damage to any units that are nearby, friendly or not. Another solution for the Siege Tank is the combination of Dark Swarm and Zerglings. Once covered with Dark Swarm, Siege Tanks will be unable to inflict direct damage (although Siege Mode will still cause considerable splash damage) to the incoming Zerglings. Nearby Bunkers will be unable to deal with the Zergling threat as long as the Dark Swarm remains over the Zerglings. Zerglings with the Adrenal Gland upgrade can quickly dispatch any Terran unit or buildings beneath the cloud. If the timing of this combined attack proves too tricky, use Guardians against enemy Siege Tanks. Their superior attack range ensures that any nearby Bunkers or Missile Turrets will be insufficient to stop the Guardian attack. Unless there are Wraiths, Valkyries or Battlecruisers nearby, the Guardians will quickly ravage any Siege Tanks present. Prevent Offensive Bunkering
A sneaky tactic the Zerg must watch for in the early to mid game is the use of offensive Bunkers possibly supported by Siege Tanks. These blockades can easily pin a Zerg colony and allow the Terran to expand unimpeded across the rest of the battlefield. Unless the blockade is broken, the Terrans will also continue to extend the defensive web into the very heart of your Brood. The best and simplest counter to these tactics is to prevent the blockade from even being built. Use Zerglings and Drones to keep an eye on the area near the colony to keep it free of any Terran presence. Should a Terran attempt to pull an offensive bunker maneuver in the late game, use Guardians to quickly smash the attempt. If you don't have any Guardians, Queens can use their Spawn Broodling ability on the SCVs constructing the Terran defenses. You can then send in waves of Hydralisks and Zerglings to crush the Terran. [ Click to Enlarge - 87 KB ]
Terrans assualt a Zerg Town using a Siege Tank and Marines in a Bunker with a repairing SCV.

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Hydralisks rush to defend the Hive using sheer numbers to overwhelm the invasion force.

Goliaths
The Terran Goliath is a deadly threat to Overlords, Guardians and Devourers, particularly if the Goliaths have been upgraded with Charon Boosters (increased attack range). The explosive antiair weaponry of the Goliath does not fare as well against Mutalisks, but overwhelming numbers of Goliaths and the long range of Charon Boosters can hide this weakness. The primary problems of the Goliath are the slow firing ground attack and the large size of the vehicle itself. Both Zerglings and Hydralisks prove effective weapons against a Goliath army. Cloaked Wraiths
Cloaked Wraiths in the hands of a competent Terran commander can prove quite a thorn in the side of the Zerg. Although Overlords can easily detect their presence, Cloaked Wraiths can also kill an Overlord in a matter seconds. If you know there are Cloaked Wraiths around, keep a large group of Overlords with your attack forces at all times. Wraiths are surprisingly fragile and are easily driven off by Hydralisks if the Wraiths cannot overcome the nearby detector presence. To provide defense for your bases, set up Spore Colonies to both detect and repel Cloaked Wraiths. [ Click to Enlarge - 92 KB ]
This Zerg player has no anti-air defenses making this setup ripe for a Cloaked Wraith attack. Place Spore Colonies and/or Hydralisks along with your other units.

Valkyries
The Terran Valkyrie is a fairly recent addition to the Terran air force, and a rather unwelcome one from the Zerg perspective. Their cluster missiles damage all air units in a target area and can quickly annihilate groups of Overlords or Mutalisks with a minimum of effort. Fortunately Valkyries are slow moving and make prime targets for Scourge and Hydralisks. Hydralisks have nothing to fear from the Valkyrie since the Valkyrie has no ability to attack ground unit. Scourge can strike Valkyries before they have a chance to unleash their missile volleys.

Irradiate
Irradiate is one of the deadliest threats to the Zerg. An Irradiated Overlord is guaranteed to die (unless a Terran Medic uses Restoration to cure it.) Tightly grouped or stacked groups of Hydralisks, Zerglings, Mutalisks, or Guardians take heavy damage from an Irradiate. Whenever a Science Vessel is spotted, destroy the blasted thing immediately with Scourge. Should your forces encounter a Science Vessel, try to spread them out to reduce the effects of Irradiate. Equip your Hydralisk horde with Burrowing to help combat Irradiate. An irradiated Hydralisk will surely die even if burrowed, but burrowing the Hydralisk does prevent the Irradiation field from damaging other nearby Zerg units. [ Click to Enlarge - 88 KB ]
Irradiated Overlords ensure that the Zerg detection abilities will soon diminish giving these Cloaked Wraiths a better chance of destroying the Zerg force.

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Irradiate can cause heavy damage to packs of Hydralisks and with this many Science Vessels, multiple Irradiations can quickly destroy the invaders.

Battlecruiser Fleets
Battlecruisers are quite possibly the most fearsome unit in the game. In large numbers they can be nearly unstoppable. To counter them, you'll need to use a combination of special abilities and your air and ground forces to defeat them. Since the Battlecruiser moves rather slowly, you should always have some time to set up a good defense after the Battlecruisers reach your outside picket lines. The Defiler's Plague will reduce their HP rapidly while a Queen's Ensnare will slow down the Battlecruisers to a snail's pace and prevent retreat. Follow up with the Acid Spore attack of your Devourers, increasing the amount of damage they take per hit and increasing their weaponry's cooldown. Finish them off with Mutalisks, or use Hydralisks protected beneath a Dark Swarm. If the Battlecruisers weaponry is already distracted with other units, Scourge can even be used. The main key to completely defeating a Battlecruiser fleet is not allowing the ships to retreat back to their home base. Should the Battlecruisers make it back safely, they can be repaired and back at full strength within a few minutes. Infesting Command Centers
It's often easy to forget, but the Terrans provide a unique opportunity for the Zerg. Should one of their Command Centers be severely damaged the Zerg Queen can infest it and bring it under the control of the Zerg. These Infested Command Centers can produce Infested Terrans bound completely to the Zerg will. Infested Terrans work particularly well when attacking lone Terran Bunkers and any other unprotected Terran structures on the ground. To infest the Command Center, simply place a Queen near the Command Center. As soon as the building becomes damaged enough, the Queen will automatically move in and infest it. Remember that as soon as a Command Center is infested, any nearby Terran defenses will immediately treat it as an enemy presence and open fire. If possible, infest Command Centers that are not too heavily defended. As soon as the Command Center is infested, lift your new building off and fly it to a safe haven where you can begin producing Infested Terrans.

Zerg V.S Protoss

Zealots
Zealots are the earliest attack unit available for the Protoss. While they are relatively expensive, Zealots can cause massive damage in melee combat. Zerglings can defeats Zealots if the Zerglings outnumber the Zealots at least 4 to 1. This ratio can vary depending on upgrades and terrain. Should you choose to face Zealots with Zerglings be sure to group them together before attacking. If a group of Zealots catches a mass of Zerglings streaming in single file rather than as a massive wave, the Zealots can take out more Zerglings than you might think. Also try to separate the Zealots apart to allow more Zerglings to attack each individual Zealot. For Zerglings to remain effective you should upgrade their Carapaces. If the enemy Zealots have an attack upgrade advantage, a Zealot will rip a Zergling apart in two attacks instead of three.

If Hydralisks are used to back a Zergling attack, the Zealots fall much more quickly. Be sure to evolve the Grooved Spines (increased attack range) upgrade. The additional range will allow more Hydralisks to engage the enemy. Keep in mind that to keep the edge over Zealots, you'll need superior numbers in both Zerglings and Hydralisks. Use multiple Hatcheries to maintain those numbers. When defending against Zealots at your home colony, have Sunken Colonies built to aid in the defense. Tie up the invading Zealots with Zerglings and let the Sunken Colonies hit the Protoss from range. In the mid to late game, use Mutalisks and Guardians to make short work of the Zealots (which are unable to retaliate against air units). Lurkers can also help tip the odds in your favor. Should the Zealots lack the support of a nearby Observer or Photon Cannon, they are easy prey for the Lurker's Subterranean Spines. [ Click to Enlarge - 88 KB ]
Sunken Colonies and Zerglings defend the Hive against a Zealot attack.

Dragoons
Although the Dragoon's ranged attack power should not be underestimated, they are relatively easy fodder for Zerglings upgraded with Metabolic Boost (faster movement) and Adrenal Glands (faster attack rate). The Dragoon's slow attack is no match for a frenzied horde of Zerglings. Unless the Dragoons have the advantage in numbers, the Zerglings will almost always prevail. Use Hydralisks to help speed up the process of dispatching Dragoons wherever possible.

In the later stages of a game, use Guardians and the Queen's Spawn Broodling to destroy Dragoons from long range. Lurkers also make a great weapon against Dragoons. With their long range splash attacks, the Lurkers can quickly shred a group of Dragoons before they can realize what is happening. [ Click to Enlarge - 98 KB ]
Mutalisks and Zerglings team up against a group of Dragoons.

Dark Templar
When faced with Dark Templar, the Overlord becomes the key unit to defeating them. Make sure the Overlord has the Pneumatized Carapace (faster movement) and Antennae (increased sight range) upgrades to unmask any Dark Templar that may be roving around. The Dark Templar melee attack is extremely deadly to any Zerg ground unit, but the attack is thankfully slow. Zerglings and Hydralisks can defeat Dark Templars, but expect casualties. If available, use Mutalisks or Guardians to attack from above. The Dark Templar has no response to an attack from the air. If there are no Overlords nearby, use the Queen's Ensnare or the Defiler's Plague to reveal the Dark Templar. Your forces can then quickly dispatch the marauding assassins.

If you suspect your opponent will use these warriors, build a few Spore Colonies at each of your bases to provide an additional layer of detection. Keep them surrounded by Sunken Colonies to help repel attacks. To further bolster base defenses, keep a few Lurkers burrowed around your important base structures and mining operation.. [ Click to Enlarge - 81 KB ]
Dark Templars can prevent an entire assault by themselves. Be sure to bring an Overlord with you before attacking.

High Templar and Psionic Storm
The deadliest weapon the Protoss have at their disposal is the High Templar's Psionic Storm. Even just one Templar with Psionic Storm can wipe out masses of Zerg units with little effort. Psionic Storm can often be the deciding factor in a Protoss vs. Zerg encounter. Destroy any High Templar on sight, keep your units spread out, and hope that you can destroy them before they have sufficient energy to unleash a Psionic Storm.

One of the quickest and safest methods of exterminating High Templar is the Queen's Spawn Broodling ability. Spawn Broodling has a long range, and one Queen can instantly kill a single Templar. Before you attack is usually the best time to use this ability. With the Templar safely eliminated, your ground and air forces can quickly take advantage of the situation to mount an effective attack. Since Zerglings are so cheap and easy to produce, they also make a good tool for targeting and destroying enemy High Templar. Even if hit by a Psionic Storm, the Zerglings can easily be replaced. If even one Zergling can reach a defenseless Templar, then the sacrifice will be well worth it. Ultralisks also serve as an excellent countermeasure for High Templar. The immense vitality of an Ultralisk will keep them alive through multiple Psionic Storms. Any High Templar is as good as dead once an Ultralisk reaches him. Avoid using Mutalisks or Guardians to attack High Templar unless you're sure the Templar have run out of energy. Psionic Storms will ravage stacked groups of Mutalisks with great efficiency, and Guardians are too slow to move out of the Psionic Storm before taking extreme damage. [ Click to Enlarge - 82 KB ]
Grouped Zerg units make perfect targets for a Psionic Storm.

Reavers
Reavers are a very powerful threat to Zerg ground forces and should be handled with extreme caution. Should you be caught in a situation where you need to destroy them, the best unit for the job is the Mutalisk or Guardian. If neither unit is available, you should instead use a combination of Zerglings and Hydralisks to take the Reavers out.

The key to destroying a Reaver is taking advantage of its slow firing rate and the Reaver's tendency to attack the first unit to enter its acquisition range . Use Zerglings one at a time and place them in front of the rest of the attack group. These Zerglings will act as bait to draw the fire of the enemy Reavers. As soon as the Reaver fires and destroys the decoy, rush in immediately with the rest of the Zerglings and Hydralisks to destroy the Reaver during its cooldown cycle. Try to arrange the Zerglings so they completely surround the Reaver and don't let your Zerglings cluster at the front of the Reaver. If the Reaver does manage to fire another Scarab, that one shot could kill every attacking Zergling. If you don't have any Zerglings around to deal with the Reaver, use the same decoy strategy with your Hydralisks. Send one in front of the rest of the group as cannon fodder, then quickly follow up the decoy with the rest of the group. Between Reaver cooldown cycles, spread your Hydralisks apart and attempt to surround the Reaver. If your Hydralisks do take fire from the Reaver, at least they'll only die one at a time rather than in entire groups. [ Click to Enlarge - 92 KB ]
Reavers can be very damaging to groups of Zerglings and Hydralisks. Surround and separate for the best chances of defeating a Reaver.

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Mutalisks should be used when Reavers have no anti-air support.

Reaver and Zealot Drop
A favored Protoss tactic is the Reaver or Zealot Drop at the back door of a Zerg Colony. To counter this strategy, build a few Spore Colonies to destroy the incoming Shuttle and a few Sunken Colonies near your Drones gathering resources. If available, also place a few Lurkers around the workers. Lurkers will almost always take a Reaver or Zealot Drop by surprise, and the Lurkers can destroy the dropped force in short order. Scourge also make a very good deterrent to drop attempts. Place a few Scourge around the back edge of your colony and order them to patrol around your resources. With luck the Scourge will surprise any incoming Shuttle and destroy the invaders before having the chance to unload.

Scouts
The Protoss Scout is one of the deadliest air to air combat units found in the game. Once upgraded with Gravitic Thrusters (faster movement) they can challenge any air force for control of the skies. They can also hit ground targets, making Scouts a very well rounded unit able to serve many purposes. To counter this threat you'll need to significantly outnumber the Scouts with Mutalisks, Scourge and Devourers, or use smaller groups of those units in combination with some of the Zerg special abilites. If you have Queens available, use Ensnare to slow down the Scouts then hit them hard with your air units and any ground forces in range. Defilers can both Plague the Scouts or provide Hydralisks with the cover of a Dark Swarm. Remember to not allow the Scouts to escape. If they can retreat back to a Shield Battery or two, the Scouts can quickly rejoin the battle at full strength. Corsairs
Like the Scout, the Corsair is also an air-to-air superiority fighter. Groups of Corsairs can make very quick work of large groups of Mutalisks, and they also make extremely efficient Overlord hunters. The Corsair's strength lies in their fast firing splash damage attack and their fast movement. Use the Queen's Ensnare to take away their speed advantage. Then use Hydralisks to destroy the Corsairs. If you have any Devourers available, use them to attack the Corsairs and increase their cooldown. Once their firing rate is crippled, use Mutalisks and Scourge to finish them off one by one. If you have neither Ensnare or Devourers to counter the Corsair, be prepared to flee. Mutalisks stand no chance against Corsairs unless in grossly superior numbers. The only chance for survival is to spread apart and surround the Corsairs, limiting the splash damage done by the Corsair's attack. Keep Overlords within Spore Colony protection and if you notice any Corsairs about, bring all of your Overlords into the safe haven of Spore Colonies. Be sure to bolster the Spore Colonies with Hydralisks since Spore Colonies alone cannot hope to fend off a sizeable force of Corsairs, especially if the Corsairs have Disruption Web available. [ Click to Enlarge - 76 KB ]
A Zerg player sets a trap for an enemy Corsair.

Observers
Observers serve as the eyes and ears of a Protoss commander and should be destroyed on sight. Use Overlords to detect their presence, then use a single Scourge to destroy the Observer before it can escape. Killing Observers on sight will help prevent the enemy from spying on you, and also help make your Lurkers and other burrowed units more effective.

Archons
Archons are the physical manifestations of Protoss psionic might and are deadly to tightly packed groups of units, particularly Mutalisks. Lone Archons do not present too much of a problem, but in groups Archons become a definite threat to the Zerg. Use Guardians to attack from afar, but don't make the mistake of approaching them over open ground. If the Guardians come within Archon attack range, they can be ravaged as easily as the Mutalisk. If you have no Guardians available, use Hydralisks and Zerglings in sheer numbers to overwhelm them. Archons are immune to the effects of Spawn Broodling and are nearly immune to the effects of Plague and Dark Swarm. Ensnare can be used to slow the Archons down, and their slowed approach can allow your Guardians and Hydralisks more firing opportunites before the Archons finally close to their own firing range. Dark Archons
The enigmatic Dark Archons are not seen too often, but when they are, be very wary. The Dark Archon possesses an arsenal of abilities that can wreak havoc on the Zerg ranging from the immobilizing Maelstrom, the Queen and Defiler killing Feedback, and the all powerful Mind Control. Maelstrom can stop any Zerg unit in its tracks for a few moments, allowing nearby enemy Protoss units to hammer your forces. Feedback can, depending on the target unit's energy stores and vitality, instantly destroy a Queen or Defiler by turning the unit's energy against itself and creating a fatal backlash. The most feared ability of the Dark Archon is Mind Control. The Dark Archon can instantly remove a Zerg force's detection support if an escorting Overlord is Mind Controlled. Even worse, should a Dark Archon capture and whisk away a Zerg Drone, the Protoss can build an entire Zerg brood under their control. All these threats make the Dark Archon a unit to be feared. However, the Dark Archon has no means of physically protecting itself. Should its energy stores be depleted, the Dark Archon becomes a very vulnerable target. Use Zerglings, Hydralisks, Mutalisks or Guardians to quickly dispatch a Dark Archon whenever possible. Carriers
Carriers are always a threat when they come into play, but the Zerg have the means to take care of them. Hydralisks beneath a Dark Swarm can do wonders against Carriers, but be sure to target the Carriers and not the interceptors. If the Interceptors can be distracted, Scourge can make excellent Carrier killers. Only 5 Scourge will take out one Carrier. Countering Shield Battery Tactics
The Protoss have no means of repairing or health regeneration. However, they can quickly recharge their Plasma Shields with the aid of a Shield Battery. Many Protoss lives are saved with the use of these Shield Batteries and the Zerg should be wary of their use. When invading a Protoss establishment, keep a watchful eye out for Shield Batteries. Should you decide to invade, make sure you have enough units to overwhelm the Protoss even if they recharge their Shields during the battle. Scouts are notorious for being avidly used in conjunction with Shield Batteries. They can quickly strike a Zerg base, retreat to recharge, then return to the frontlines for more combat. To prevent this type of tactic, attack the Scouts with Mutalisks, Devourers or Hydralisks at an angle that blocks their escape route to a Shield Battery. Hopefully you can destroy the Scouts before they can retreat back to safety.

Zerg V.S Zerg

To defeat another Zerg brood, you must know the full extent of the strengths and weaknesses of each unit and structure. Since you and your enemy both have the same units and strategies at your disposal, expect a fiercely fought combat. Production speed is extremely important, as is the manner you decide to develop your Brood structures.

Overlord Scouting
Early reconnaissance with the first Overlord is a risky tactic, but the tactic can really pay off. If you can find your opponent early and see what they are building, you'll be able to adjust your own building order to properly counter or exploit the enemy's starting tactic. This provides you with an important, tangible advantage over your enemy who does not have this information. Once over your enemy's base, your Overlord will not have much to fear until your foe begins producing Hydralisks or building Spore Colonies. At this point your Overlord should retreat to a safe distance as soon as possible to avoid being destroyed. The drawback of early Overlord scouting is the possible revealing of your position to the enemy. This gives them the opportunity to plan an offensive or defensive strategy of their own based on your location and what you could do from those starting spots. Two starting locations very close to each other usually results in a brutal Zergling rush fest. Starting spots that are a little further away usually results in Sunken Colonies being built, then both players traveling up the tech tree. Early Game Disruption
One of the quirks in a Zerg vs. Zerg encounter is that every player can build on each other's Creep, even the enemy's. If you can quickly find the enemy with an Overlord or Drone scout, you can send your own Drones over to your opponent's Creep and begin building Creep Colonies. With this tactic you'll need a quick Spawning Pool to convert those Creep Colonies into Sunken Colonies. If done quickly enough, you should be able to severly hamper an opponent's early game build and strategies. Burrowing
The ability to burrow can be very effective all throughout a game. You can use it to save your Drones when your resource areas are attacked. Once your defending units have secured the area, the Drones can unburrow and continue their work. You can also use it to quickly burrow Zerglings around the map to keep an eye on key expansion locations. Burrowing can also be useful for ambushing enemy forces, hiding extra Drones at potential expansion spots, and protecting valuable ground units such as the Defiler. Watch for enemy Overlords that may be searching for burrowed units. Should a burrowed force be attacked while underground, they face a slight disadvantage. Unburrowing takes a small amount of time, and during this time your units are vulnerable to attack. Zerglings
Zerglings are the first available attack unit for the Zerg. With their extremely low cost and ability to spawn in pairs Zerglings can terrorize enemy colonies very early in a game. Their power comes from their sheer numbers, and when upgraded with Adrenal Glands (faster attack rate) and Metabolic Boost (faster movement) Zerglings are truly an awesome combat force. If built in very large numbers (100+), Zerglings can be used to completely flood an enemy base and tear everything down in a very short period of time. Even Hydralisks, Mutalisks, Guardians or Ultralisks have a difficult time dealing with such an immense number of Zerglings. To counter a "flood" tactic of that magnitude, use Lurkers as your primary counter unit. Their Subterranean Spines can rip through entire waves of Zerglings before the Zerglings can get close enough to cause major damage. If Lurkers are not available, you'll need masses of your own Zerglings supported by Sunken Colonies, Hydralisks, or Mutalisks to fend off that type of attack. Use choke points to your advantage when stopping floods of Zerglings, as using favorable terrain may sometimes be the only way to stop a massive Zergling rush. On open ground where the Zerglings can surround and outnumber ground units five or even ten times to one, Adrenalized Zerglings will definitely have an advantage. In most land based maps, you will want to continue Zergling production throughout the game, not just at the beginning. Combining Zerglings with Dark Swarm is another extremely useful tactic and if your opponent is using Hydralisks or other ranged attack units to make up the core of their forces, Zerglings covered by Dark Swarm will make quick work of them or remain protected while razing an enemy base. [ Click to Enlarge - 86 KB ]
Zergling vs. Zergling encounters are fairly easy to manage - the player with the most Zerglings and/or upgrades will almost always win.

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To counter Zerglings, use your own Zerglings (making sure they have more upgrades), Mutalisks or Hydralisks. A mix of Hydralisks and Zerglings can generally overcome an enemy who is using only Zerglings.

Hydralisks
As the most versatile ground unit for the Zerg, the Hydralisk appears in almost every Zerg battle. Understand all the strengths and weaknesses of the Hydralisk so that you can exploit them to your advantage. For more details, check the Hydralisk section.

Probably even more so than with Zerglings, having the clear advantage in Hydralisk numbers will determine the outcome of a Zerg vs. Zerg battle. In addition to just relying on sheer numbers, a wily Zerg Brood will use their Hydralisks creatively to gain victory. Set up choke point ambushes with Burrowing, use them to drop on the enemy from behind, or maybe use them as a decoy force so that units like Mutalisks or Guardians can accomplish a task elsewhere. Use the versatility and usefulness of the Hydralisk to the full extent and they can save you in any Zerg vs. Zerg encounter. Stopping Hydralisks can be a little tricky, particularly in ground battles. Use Plague, Ensnare, and Zerglings with Dark Swarm cover as often as possible against masses of Hydralisks. If you have Mutalisks or Guardians available, use the terrain to your advantage and attack from over ridges, water, or space to dwindle their numbers without taking massive return fire. Lurkers
Lurkers are excellent tools against the other Zerg ground units. They can tear Zerglings and Hydralisks to shreds and even the mighty Ultralisk has something to fear from the Lurker. Use them for colony defense and ambushing invading forces at choke points or high ground ramps. The one drawback when using them against other Zerg is that any Zerg opponent will typically have an abundance of Overlords to detect a burrowed Lurker. Once detected, the Lurker is vulnerable to air attack from Mutalisks and Guardians as well as the Spawn Broodling ability of the Queen. Mutalisks
Much like the Hydralisk, the Mutalisk is also an extremely versatile Zerg unit, only the air is the Mutalisks' domain. Mutalisks are not hatched cheaply, but their ability to fly and attack both ground and air proves most useful in a battle between Zerg broods. Keep several pairs of Scourge with your Mutalisk groups at all times on the chance that they run into an enemy Mutalisk group. The Scourge will help tilt the tide of battle in your favor. Should your opponent build masses of Zerglings, Hydralisks, and defensive Sunken Colonies, your best bet will be to build Mutalisks. First take care of any Hydralisks and Spore Colonies present then finish off the rest with relative ease. If the Hydralisks outnumber your Mutalisks, use your enemy's structures for your own benefit. Maneuver your Mutalisks in circles and pick off Hydralisks one by one as they try to make their way through their own base. If you have the advantage in numbers, just get it over with and attack the entire force head on and continue with the razing at your leisure. Mutalisks tend to tightly stack when attacking a target and are particularly vulnerable to area affect attacks or abilities. Ensnare, Plague and Devourer Acid Spores can all quickly affect your entire Mutalisk horde. Dark Swarm covered Hydralisks can also be deadly to Mutalisks over open ground. While Spore Colonies can deal significant damage to Mutalisks, the Colonies must be built in large clusters to effectively repel a large Mutalisk group. If the Spore Colonies are spread apart and not all in range of each other, large Mutalisk forces can pick them off one by one from the outer perimeter to the colony core. [ Click to Enlarge - 87 KB ]
Mutalisks are the perfect counter to Zerglings.

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Hydralisks and Spore Colonies fight fiercely to prevent Mutalisks from overcoming them.

Scourge
Scourge can be the key in a heavy air based battle. They can quickly destroy an invading Guardian force and any Devourers that may follow as escorts. Scourge make the perfect Overlord killers. Depending on how closely your opponent keeps his population count to the population limit, Overlord hunting with Scourge can quickly cripple an enemy's unit production. Scourge do not work as well against large groups of Mutalisks, especially if the Mutalisks are well managed. If an enemy Mutalisk force is distracted by your own Hydralisks, Mutalisks or Devourers, then the Scourge may come in handy to destroy Mutalisks one by one.

If you opponent uses Scourge heavily, the best counter is Scourge hunting with a few of your own Mutalisks or Overlords. Use the Scourge's quick tendency to auto-acquire enemy targets to lure them into traps or suicide traps. If more than two Scourge impact and destroy an Overlord, your enemy has wasted a large number of Scourge. Quick moving Mutalisks can also lure Scourge over your own Hydralisks and Spore Colonies. Since Scourge require extensive Vespene gas to produce, causing your foe to lose Scourge in such a fashion can be quite painful to your enemy's economy. Overlord Hunting
The Overlord serves many different fucntions for the Zerg and should be protected whenever possible. Unless you have a definite need for early scouting, try not to send Overlords out by themselves. This makes them particularly vulnerable to Overlord hunts and every time you lose one, you lose eight control units, a potential transport, and a detector. Keep them within the safety of Spore and Sunken Colonies or with an attack force adequate enough to protect them. One thing NOT to do with Overlords is try and hide them in a corner of the map, hoping the enemy will not notice. Most experienced players will find them and left unprotected, you can lose an entire group of Overlords in a matter of seconds depending on the attacking units. On the flip side, if your opponent disregards the advice above, take every opportunity to hunt down any stray Overlords your enemy might have around the map. A pair of Scourge can destroy an Overlord before your enemy realizes what's happened. Packs of Mutalisks can quickly travel around the map and eliminate any unprotected Overlord presence with ease. [ Click to Enlarge - 75 KB ]
Mutalisks go Overlord Hunting.

Queens
The Queen's abilities are quite useful against other Zerg broods and should be used at every opportunity. Since most Zerg units travel in tight packs, they can be ensnared en masse, making the units ripe for attack. Enemy Ultralisks or Hydralisks can be easily dealt with using Spawn Broodling. Parasite is extremely helpful when trying to keep an eye on enemy movement and unit production. Use Parasites on Overlords to gain their detection abilities, especially on Overlords in enemy bases protected by Lurkers. Parasites can also keep an eye on any transporting activity of the affected Overlord. With a few fully charged Queens, you should be able to Parasite the majority of an enemy's Overlord population.

To deal with enemy Queens, the best solution the use of pairs of Scourge to pick the Queens off one by one. Mutalisks also work well as Queen hunters, but they run a higher risk of being hit by an Ensnare or being parasited. Guardians
Guardians are a typical unit used when breaking into a well defended Zerg colony. With their long ranged attacks, Guardians have little to fear from defending Spore Colonies or enemy ground troops. They do, however, need to worry about any Mutalisks, Scourge or Devourers that may be nearby. For that contingency, always keep your Guardians escorted by Mutalisks, Scourge or Devourers of your own. Devourers
Devourers are an excellent answer to enemy Mutalisks. Their splashing Acid Spores can seriously cripple a group of Mutalisks, making them vulnerable to attack from your own Mutalisks and Scourge. Devourers also work very well against Guardians, slowing down their attacks before the Devourers can finish them off. If you need to deal with enemy Devourers, Scourge again prove to be the best answer. If you can catch the Devourers over open ground, you can also use Hydralisk groups to destroy them. If using Hydralisks, position your horde beneath the Devourers before opening fire to cause the most damage possible before the Devourers can escape. Ultralisks
Ultralisks can be quite fearsome, especially in groups. Use them to take down enemy Sunken/Spore Colony defenses, ravaging packs of Zerglings, or Hydralisks. They are unaffected by Dark Swarm and Plague is not as devastating to Ultralisks and their 400 hit points. Enemy Ultralisks can be easily dealt with using a Queen's Spawn Broodling ability. If Queens aren't available, use Mutalisks and Guardians to destroy Ultralisks from the air. Nydus Canals
In the late game, Nydus Canals become a key threat for both sides. Their ability to quickly transport units from one location to another can nullify the mobility advantage a Mutalisk force possesses. One of the strange properties of the Nydus Canal is its ability to be built on anyone's Creep, friendly or not. In the case of the Nydus Canal, all you need to build the exit node is to see the enemy Creep. Using this tactic, you can invade their base from within using all the ground forces you have available. This can be especially useful on "island" maps where transporting large numbers of units can be tricky or impossible if your foe has a superior air force.