I use my zip drive to reinstall windows, etc..as a startup disk and regular floppy. There are a few things I had to do..
1. Unplug your floppy entirely...
2. Zip MUST be on Master
3. Bios has to be set to boos LS/ZIP as the first device, not floppy. (LS/ZIP, HD, CDROM)
Works fine for me, I have a Zip 100 IDE though.