You can't simpley unlock them, you have to buy them.
I'm pretty sure that you just have to beat the game to get it
You receive an achievement and you unlock the first Nazi zombies level, nacht der urden.
Beat the game on any difficulty.
You go to the terminal and punch in DOA you'll unlock a level called dead ops arcade (the last level)
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 unlock "five" the pentagon level for zombies. you also unlock the dead ops zombie arcade game.
If your talking about typing codes into the computer when you break out of the chair at the main menu, these are the codes: Unlock Dead Ops Arcade in Zombies: 3arc_DOA Unlock all Zombie Maps: 3arc_unlocks
u get it by playing through about 4 days woth of level, it is awsome
You can get the mystery zombie by replaying the campaign till the conveyor level of the fog stage (level 4-10)
just keep killing them by shooting them are knifing
You need to be on level 13 to unlock the second sws mission on binweevils from blah head (on binweevils broth)
No, if you beat the first level in campain, you can unlock the first zombie level. But, to unlock the others, you either have to beat the campain or, assuming you know how to break out of the chair, break out of the chair and go to the computer and type in, 3ARC UNLOCK