Please learn from my mistake. Or error.
If you have installed an ATAPI Zip in your PC, then make sure it is not jumpered as a 'Floppy'. If it is, you won't be able to read Zip disks when you swap them between PC and SCSI E-MU - E6400 Ultra in my case. EMU will see them - maybe - as "FAT??" or worse - hang on boot! :-(
Silly me. I thought I'd bought a duffer!
Regards
John