I found your quixplorer and it's a great tool.
(Your beta zip functionality doesn't works at my site - sorry.)
But I need the zip functionality and so I look for a free zip library and found it.
Find attached a small sample application for creating zip archives and unzipping them again at a webserver.
It will be very nice if you can integrate this into your quixplorer.
Sample application for zip and unzip.
You will find the documentation for pclzip at:
http://www.phpconcept.net/pclzip/index.en.php
and additional for pcltar at:
http://www.phpconcept.net/pcltar/index.en.php