Um from looking at the code I think it may be Zserver not Zpublisher doing it. I think there is code which set up the CGI env vars at Zpublisher pick em up and works with them, so it is the code that sets those GCI vars that is dropping it. Isn't it tru that if you use APACHE, they are set by APACHE and is you use Zserver w/o frontending it with APACHE something in Zserver has to be setting them?

That sounds reasonable. I'd imagine it would have something to do with PATH_INFO, PATH_TRANSLATED, or SCRIPT_NAME. Have you looked for calls to the Python cgi module in ZServer? I might start by looking for it trying to assign these environment variables to see what it does. Sorry I can't give you any more specifics.