About the requested feature (having zip support even if zip is not available). Some users seems to have already some code about it (http://gallery.menalto.com/node/41670 and http://gallery.menalto.com/files/zipcart_profix898_g21mod.zip). Would it be possible to merge their code with the official module ?
Bugs
1. Found a "bug". ZipCart does not use the php-temp-directory but "data.gallery.tmp" without checking if it exists or is writeable. In secure environments ZipCart does not have the right to create this directory (does it even try?). When trying to download a cart, you just get no Download and the cart is empty again. The problem is, that ZipCart does not throw any error (meaningful or not), so somebody unable to edit ZipCart to get some debug output has no possibility to know, why no download is offered. It would be a good idea to add something into Download.inc at line 46 to check, whether "data.gallery.tmp" exists or not.
