All one has to do to unlock Call of Duty Mobile's Zombies mode is reach level 5 through playing the rest of the game normally. Once that's done, players are free to play the mode as much as they want while it's available.

Overview. The Biggest Zombies Experience to Date: Call of Duty: Black Ops II Zombies features three different ways to survive the zombie apocalypse. Unravel the mysteries of a dying Earth in Tranzit, fight endless waves of zombies in Survival mode, or compete in the new 4z4 last-human-standing mode, Grief.