Is that a Zip 100 or a Zip 100 Plus? If the first, I would check to see if termination is enabled. If the latter, the 100 Plus should enable termination automatically. Next, make sure that the Zip and EN/SC adapter have different SCSI ID numbers. Finally, try turning both external devices on first, then power on your Mac. It should boot normal from there.

73s de Phreakout. :rambo: