I haven't used mod_deflate myself, but my understanding is that it compresses each individual request, rather than putting a set of files in one zip file that are all sent together as one request.
The advantage over mod_deflate is that you have the latency for only one request of perhaps 100's of files, rather than the latency on each file for the site.
Right. The server can immediately know all the files that the client could need (and with some coordination.. does need). The client though has to get the first one to learn what others it may need, then request those.. and those may require more. Each level of recursion costs you at least 1 round-trip latency, likely much more due to the links not being at the very top of the page, the server not being instantly fast, and the browser's rules for requesting things.
