rather than put the original version of the maps, like dust2 etc, maybe you could put dust2 maps that is designed for zombie server..
idk if there is such version in css but i know there is for cs1.6..

the problem is zombie in cs 1.6 is quite different with css..
in cs 1.6 u can actually kill the zombie alone, but in ZR, im afraid thats quite impossible, except if the zombies are so dumb...
and even in modified dust2 thats designed for zombie server in cs1.6, i would find it hard to def against zombies, since zombies regen hp when they kill someone, and their have big hp