Very fun game. Test it:

http://www.sigma-team.net/games/action/zombie-shooter-2.html

do you know if it's playable cooperatively over lan? I couldn't find any info regarding that on the site.

I don't know. I couldn't find in game menu :-(

I actually was able to finish that game, it was fun, really addictive, and one has to be fast running while changing weapons(you'll eventually run out of ammo). For me it’s a fast phase strategy game. Familiarity with the Map would really help, as well as knowing those fake walls wherein they store weapons and ammo's.