If the condition warrants and the price is reasonable, my particular preference would be the ZKK, just because I have a love of classic models, but I can't give you an objective comparison between the CZ and the ZKK. However, our good friend Joel Dorleac weighed in with his opinion in a post from 4 years ago:

http://forums.nitroexpress.com/showflat....true#Post280745

Bear in mind, of course, that Joel's standard of what is an acceptable "working rifle" is likely to be rather higher than most of the rest of us!