I'm saying that there's a /czero/ as well as a /cstrike/ directory when CZ is installed. [img]/forums/images/graemlins/smile.gif[/img]
So indeed it seems that you get an upgraded CS installation. I'm not sure what measures have been implemented by Valve to prevent people from simply giving out the updated assets. I suppose it would be possible to have Steam check this kind of stuff and ... correct it, if necessary.