Pretty sure they're zipping for the encryption, not the compression.
edit: the way I'd solve the rest is just by using a torrent magnet link. The problem with that is that you might have to teach someone how to open a port for UDP traffic, but after they've done it, sending files of any size to them becomes trivial.
edit: the way I'd solve the rest is just by using a torrent magnet link. The problem with that is that you might have to teach someone how to open a port for UDP traffic, but after they've done it, sending files of any size to them becomes trivial.