According to this article, using a zune with an xbox 360 should be easy.

My xbox 360 is up-to-date, but when I plug my zune into the front usb port, nothing happens. The zune screen lights up because its charging through the usb port, but that's it. If I go into the Pictures/Music/Video, I can't switch devices to the zune. It does however want to sync with my zune data (from my Vista laptop) over the wireless network.

Does anyone have any ideas?