They also made SCSI ZIPs - used on Macs and SGIs, etc. The parallel models
used a proprietary SCSI over parallel protocol, at least on the early ones, and
were slower than snails. I've never popped one open to see if it is possible
to revert to SCSI, though (probably not). I think I heard that later models
used an encapsulated IDE protocol. I'm not sure if it is still the case, but I
think some of the old (2.2.x) Linux kernels had some documentation about the
protocol.
It could be possible to hack together a similar interface for floppies,
though (encapsulate over parallel port)