Instructions
Play with three friends. You can play zombies mode alone but it's more difficult to watch all angles at once, especially when you have many rooms open at the same time.
Repair windows and doorways. Zombies break through windows and doorways each round to get to you and your teammates. At the end of each round before the next wave of zombies comes, repair all entrances. It takes zombies longer to reach you at the beginning of the next round and you'll also earn points for repairing to apply towards new guns, ammunition or opening new doorways.
Communicate with your team members to discuss a strategy. Don't open new doors without consulting your team first to let them know the zombies are coming from more directions. As a rule, the less entrances zombies have to come through the easier it will be to fend them off.
Share kills with your team. Zombies is a cooperative game mode. Your team members need to earn points from kills to help fend off the zombies and open doors. If you get knocked down, a player with a pistol probably isn't going to be able to revive you.
Knock one zombie down to the crawling level but don't kill him just yet. Run around and repair all the windows, reload your weapon and purchase a new one if desired. Then, kill the final crawling zombie to move on to the next level.