Zerg Strategy
The Northern Vietnamese army in the Vietnam War used the strategy where they would mass and overrun, similar to the tactics used by most zerg players they mass and attempt to overrun. Now a true zerg professional on a money map will be able to continuously attack your base non-stop. Your defenses will be constantly under attack, so the key to avoiding this situation is to hit them before they hit you.
From the start of the game if you zealot rush a zerg player they will be handicapped if they do not die, you should not allow zerg players to breath you have to send units to make them produce defense and not allow them to make 20 hatcheries and mass up. If you allow a zerg player to set up there base they will have a certain amount of lurkers at there choke and hydralisks behind them to draw the fire. To counter this effect you can either use reavers or high templars. High templars are the most effective as when 3 psi storms hit the lurker location they will be finished an extra 3 psi storm on the units behind will destroy any zerg ground unit and any air units as well. So once you take 3 high templars and psi the lurkers and the units behind them your main army will have easy access to there base. When you enter a zerg base they will have scattered lurkers and mass zerglings will be produced. You will need observers and dark templars to take out the zerglings as dragoons will crumble to the mass of zerglings. Also the dark templars will not last against lurkers or any ground attacking air unit.
If a zerg player attacks you they will come in one of 3 ways mass ground assault, groups of guardians, or they will attempt a drop. To counteract a drop is easy as any unit that is dropped will die under a psi storm, so 2 or 3 psi storms where they drop will take out the entire army dropped. Guardian groups are usually escorted by either devourers, mutalisks or scourge. If you have air units available you will need at least 12 to mount a counterattack, corsairs or scouts are the air units of choice. When they attack the guardians will be attacking your cannons or buildings. So with air units you need to lure there escort to your cannon group and hope that enough of your units survive to take out the guardians before the next escort arrives. If you have a arbiter it would be great because if you stasis there army they will not be able to produce any more units so an attack on there base would be simple, but lets face it most players don’t have arbiters sitting around. The easiest way to counter guardians is to have a few dragoons draw there fire while you sneak up 3 psi storms, the entire group of guardians will be killed or easily disposed of. A massive ground assault is the most common and usually never fails; this is because protoss players are unaware of how to make an entrance defense. To make an effective choke defense it requires the use of cannons reavers and high templars with maybe a few dark templars and dragoons. When you have 4 or more reavers order them to attack the choke and hold position them behind cannons this way the scarab they shoot goes through the cannons and hits the mass of units attacking your cannons. One shot will severely weaken the opposing enemies if they are not destroyed. High templars are used if your reavers are unprotected by the cannons and dragoons and dark templars just to finish them off.
Keep in mind that the zerg are quick to rebuild and massive losses do not affect them much, if you face an expert they may try to destroy your main nexus with upwards of 24 mutalisks. A whole bunch of cannons will kill them off but not before your nexus is gone therefore it is imperative that you have charged high templars ready to strike against them, only high templars or mass air units will be capable of saving your nexus.
To recap the best way to deal with the mass units that zerg produce is with high templars or reavers, this is the way to counteract the strengths in there race but you still need to take advantage of the weakness of there units by use of divide and conquer. When they arrive out of the egg they are divided so you need to conquer then.