Z Com: Enemy Undead is an achievement that can only be won with the Necroa Virus DLC.
How to get this achievement?
Zombies must destroy a Z Com base to earn this achievement. Z Com bases are destroyed by zombies. To destroy a base, a player should upgrade zombie fighting strength and insure that there are many zombies in the country with a base. It is also worth noting that the less time a Z Com base has to develop, the weaker it is, and the easier it will be to defeat it.