I use WinZip to zip entire directories of code and send them to a fellow programmer. He makes changes and sends the directories of code back to me. Ignoring the fact that this is not a good way to keep the code clean when we are both working on it, I notice that his zip files are far smaller than mine, with basically the same data inside (mine range around 36,000 KB, his 2,000 KB). I believe he is also using WinZip. What's going on here, and how can I make mine "more compressed"?