I find myself seriously doubting that it's possible to 100% the New Game+ version. I practically carpet-bombed Eskimo Town just to kill the 40 hazmat guys, with fully upgraded zombies, and even then it still took WAY longer than 30 seconds to finish them off. It really doesn't help any that the game stats cover up the top left corner of the play area, so you can't click there to drop support.
Aside from that, the game is great as always.