Are you sure you’re looking in the right place for the firmware? Here’s the Zip firmware thread with the needed instructions, and the download link is the second one there–the one that says, “Manual Firmware Update (All Regions) - Click here to download”.
http://forums.sandisk.com/t5/Sansa-Clip-Zip/Sansa-Clip-Zip-Firmware-01-01-21/td-p/297767
