There are two version of those Zip drives, the normal one and the "plus" version, that actually says Plus in yellow on the front.
It has also a switch in the back to select the id from 5 to 6. That one works both in parallel mode and in SCSI mode with the same cable.
Regarding PCMCIA booting, ca I hook a Flash hard disk there and use it as a hard disk, or only ram/rom cards work there ?