In case you weren’t aware, there is a secret Zombie round at the end of the Tier 4 map “Riot in in Exo Survival mode in Call of Duty: Advanced Warfare.
If you didn’t know that, I guess you wouldn’t be here though.
Anyway, check out this guide first if you need help unlocking all of the Tiers in Exo Survival mode.
How to Unlock the Secret Zombie Round in Exo Survival
In order to access this special zombie round, you need to complete round 10 on the Riot map, which is the only map available in Tier 4.
Once complete round 10 on Riot, you’ll see a special cut-scene, and all enemies on round 11 will be zombies.
Finishing round 11 will also unlock the Exo Survivor achievement/trophy.