Heli Attack 3/Zone 3-2

Helicopters to destroy: 12 Helis 5 respawning Gunned Robots

Tactics
You can use the same tactic i mentioned for zone 2-4 that should do it. If you get too much damage in the game, try using the better weapons you got earlier, and don't mind wasting firepower(not of course wasting the blackhole, the taser, a-bomb,soundwave, bladerang or anytime; because blackhole, taser and a-bomb guarantees a one shot kill on every heli and using soundwave would be a waste of so high firepower because it has really high kill rating with attack helis, and others are effective much ONLY against attack helis)