No point in zipping a Divx AVI because the file would be larger, not smaller.
The only thing that would work would be a RAR archive, but again theres no point.
a DIVX encoded avi is about as small as it will get, and i'm not sacrificing image quality. I find it SO annoying whenever i waste about half an hour of my times downloading an AVI file and all I see is a bunch of blocks because someone put download time and size over the quality. Graphics are there to be seen - and if you can't see them the way they are intended to be then its all kind of pointless, don't you think?
Im on 56k as well, BTW.