I went to the hatcheries south-west personally, not so defended.

There are 3 there, I killed them (do not kill all the drones), moved back a bit, waited 30 seconds and move back in, they are rebuilding one hatchery, destroyed it when it was still under construction and got achievement.

It took me 3-4 tries to get my timing and economy start setup but it's not impossible
If you doing it for achievement, screw the initial base and bring all your troops with you.

@fries hehe the helions worked! those far-far away ones i just sent 4 helions to suicide on the probe. the most annoying part is that when the 'toss have a mass of units around, it's hard to right click on the small probe ...

no that is not, i able to destroy all, try again, when the game start, add more scv with harvesting, withdraw and sell of your outer bunkers, just defend on higher ground, , create another bunker there.

Got benefits at higher ground, only 1 entrance and they cant attack until they see you. so defending wise will be alot easier, mass produce marines and supply depots, you should know that by pressing the shift key u can order scv to queue building, set hot keys(ie ctrl-9) on all barracks, always remember to watch your unit count and keep supply depots up. use hot keys to train marines. also upgrades for marines are very important, even its only level 1.

after rescue 2nd batch of soldiers, you should have enough fire power to start attack them, start with top left base, keep making marines with hot key, dont spend too much time on your base, micro management is very important. when only front few marines capable to shooting at target and blocked others, move them all in front b4 start shooting, might lose some marines but save you alot of time.

Do not think you have 20 mins, the last few mins cant count cause there are plenty of zerg ejecting out, if you just want to achieve 4 hatcheries, just do top left and the left 1, top right 1 is much harder, 2 hatcheries each side.

did few more games on insane, its quite easy using the trick on terran especially you know their pattern. got ~200+ achievement points from there =P

i noticed after u drop a cannon, the marine will attack that cannon, but then drop a pylon closer to them, they will attack the pylon, then u drop another cannon nearer again where they will attack this nearer cannon, then the 1st cannon completed, they move away after die trying to kill it, then i continue to drop pylon and cannon. within few drops, im attacking their scv mining operation d, fastest 1v1 insane like 4 mins, fastest 2v2 insane 5min17sec =P