You have to beat a certain about of levels in adventure mode and then you should unlock it
If you have Windows 7 you have Plants vs. Zombies for Free
stuff
No you can not unlock the zombie levels by playing co-op you can only do it by playing single player. Also if you play certain level in campaign you will unlock levels for zombies.
you have to think it no way you can have plants vs zombies with a secret code you have to download it
just keep playing you will get it on one of the night levels 2-1 2-2 2-3 one of those levels i think
You don't
i need help to get zombatar
get the unlock code
In every level you pass, you unlock another plant you can use in different levels. You can also buy them from Crazy Dave's shop, Crazy Dave's Twiddy Dinkies with coins you get from zombies and the other game modes, you can also buy upgrades for plants to make them extra effective.
Buy the game..lolol
you have to hack it.