Zombie Attack mod for the Delta Force Xtreme FPS game made by Novalogic inc.
ZA is a mod that put zombies in your way.
You can play LAN cooperative matches with capacity up to 64 players,
You can even play TDM maps as a Survivor with all the weapons or as a Zombie.
This mod can be played online with TUNNGLE, a VPN program that creates virtual LAN networks to play games like this. You can use Hamachi as last resource.
Check this gameplay: