Be aware I last won the map 2 versions ago and thus some things may have changed. Although I never won past the easiest difficulty, harder difficulties just require you to farm kills more (double time to complete for each difficulty up. A good run should take only 2 hours odd (ingame time).
The whole key is ghosts, immortals and siege tanks/colossus.
Immortals with their 100 energy and hardend shields are the only units which can tank a considerable number of hits from crazy kerrigans from construction. Behind a healer they are physically invinsible unless over focused (too few) so you can use them to farm spawns.
Ghosts will make your primary kill squads for buildings and bosses.
Siege tanks (or colossus, but tanks are still good if not better) are used to kill spawns and provide support. If available replace them with stone zealots due to their AoE and AA capabilites as well as insane DPS output.
You will also want to make a hero unit, this is a unit which gets most of your kills for you so has insane HP/shield, damage and armor. You will want a nippy unit for improved survival which has high killing power to take advantage of linear damage growth. Maurder is a goodone due to AoE nuke but will have problems getting kills although pros did advise its use at one time. Other good ones are firebat and hellion. High templar can nice as well but requires early use to avoid losing out on kills. Bad ones are melee or slow attack speed single target.
The Ultimate ones are the colossus, the stone zealot and the reaper. Colossus is good anti ground with splash. Stone zealot is a better colossus in nearly every way (even hits air) making it a very good hero. Reaper is the ultimate anti land hero and can single handidly do large parts of the map as it has crazy long range pierce attack that can even kill stuff without them counter attacking as well as its high mobility.
Firstly, start by farming kills till everyone is 100 with all 5 techs (2 if you do not have access to protoss). Then move to farming suprize spawns using immortal wall to soak the kerrigans. Push through the first part killing all spawners one you got 1 million minerals odd each. Use vulture turrets against the infested marines or psyonic storm if you got templars. After whiping out the left main spawn, you must face the infinite hydralisks. Your hero unit should easilly solo this (my reaper was taking 0 damage and its splash pushed easilly). Then comes the top right spawning crap, uses ghosts to clear it and before you kil the last hive, send all ghosts to the left so that when livithan spawns you can attack him from behind while your hero units soak up the infinite spawns (watch that livithan does not focuse them down).
Now the map gets harder, send ghost armies to clear badies along the top of the map as you go left. You will eventually encounter the ultralisk boss which is a good one to farm and power your heroes / get a million minerals again from due to its infinite spawns. Once done, use ghosts to kill and move on. You will need to eithor be very suicidal and charge the brutalisk boss down with ghosts or get a few high templars to kill the infinite spaawning infested marines while ghosts eat him. Finally is the queen which spawns none other than infinite kerrigans (ouch). Line the wall by her with siege mode siege tanks to handle the infinite spawns and then send ghost armies (or your hero if he has 6000 kills odd) to lure the queen into the front where the tanks and ghost armies can easilly surround hero without spawns and kill.
Welcome to part 3 of the map (which is entirly different on another unseen area of the map which is meant to be underground).
Firsty you must kill all hives, spawmming ghosts works well but be warned that infinite banlings spawn from the left when near so cloak and do not shoot and use immortals at the bunker to take all their suicidal hits. Now you will have to kill some crazy guy using the 3 laser drills before he kills the bunker (only drills hurt him) but he should die fast and ignores your troops and does not hurt them.
Next up is killing the overmind tendrils. You have to attack them all at once to be able to kill any of them but once one dies, they all will die easilly. Use dark templars for this if you wish but be aware they are obsolete for the next part (not too many). Now for the final boss, the mighty overmind. He will appear at the far top of the map once any troop reaches there. He will charge up some mega powered (which never was used on me I kill him so fast lol) ability but if you fire the 3 drills, a huge number of ghosts (move them infront so more can shoot) and your heroes at him he should die in no time.
Over now? Not yet as now is the final part, the escape while meteors rain death on you. You get bonous score for every unit that lives so start by moving them from the spawn point as fast as possible (as 1 meteor could kill most in 1 hit). If you are cunning and save a SCV you can make a tunnel and warp to the ship with nearly no losses (the tunnel can take 3 meteor hits which is very rare in the same spot) and then salvage it to minimize losses. Your hero units are so tough at this point in the game that even multiple meteors should not damage them noticable (even a 1K unit can take a few).
Once everyone is on the ship (all units must be onboard for all players), you leave this damn hell hole and finally win the map. Congratulations, I only have won twice.
I have no idea what the makers were thinking, producing something that needs so long to finish. High difficulties can take as much as 20 hours I heard.
