I beat it finally.......10 levels....Just upgrade The Bozookas, cash max level and production levels and throw those zooka men out there like crazy....by level 4 you should have enough levels to escort that stupid truck driver and then the choppas don't have a chance with your bazooka men.
I give up on level 4.........how the heck do you beat it!?!?!?!?!?!?!?!? I've tried everything leveling up my zokkas, my heavy tanks, etc. I've tried to trick the helicopters by producing mad ammounts of tanks but that dang rescue truck goes soooooooooooooooo sloooowwwwwwwwwwwwwwwwww Arrgh. >=/