Incidentally, the early parallel port ZIP drives were really SCSI drives that had a parallel port to scsi converter on the board. Not that you could do anything cool with them, but pricing them lower than one with a SCSI interface is understanding the marketplace rather than anything else. The SCSI drives had two extra switches on the back, but used the same db25 connectors as the parallel port drives. People with Macs and other SCSI users were used to paying more.

I know there was a later revision parallel port ZIP drive that wasn't internally SCSI and that might have been lower cost.