After all the speculation on zombies in Call of Duty: Advanced Warfare, at launch, there’s no fourth mode in the game. Zombies, which was shown in the Cut Scene video earlier, is a bonus wave in the Exo-Survival mode only on Riot map.
According to players, it actually takes a lot of work to even unlock Riot to play on it. After that, you have to get to the certain round to play against the zombies, which then it ends in a Cut Scene.
Earlier today, GameStop stated Zombies are coming in Advanced Warfare DLC; it still isn’t clear whether its a fourth mode or just more Exo-Survival maps with bonus wave.