Hi Jerry,
While I don't have a zune myself, from what I understand it plays back files in the MP4 (mpeg-4) format
Again, while I don't have a zune personally,
Replay Converter can convert to this format, so that should do the trick for you.
On another note, I usually use RC to convert to my psp, my ipod/ iphone, etc and it works like a charm!
Hope this helps
