[kadet.89]

For v34 these versions, in my opinion, are the best options:
ZombieMod 1.2.8 (has no zombie classes)
ZombieMod 2.0.0
There is also a version of ZombieReloaded plugin, but it doesn't provide the same settings and the gameplay is like in CSGO.
For newer CS:S versions there was ZombieMod 3.0.0, not sure if it is compatable with the latest CS:S version though.