If you pull/throw out the dead internal SCSI HD, it will automatically boot up off the external Zip (with operating system installed), sans an extension. Alternately, pressing Command+Option+Shift+delete during bootup causes the Mac to ignore SCSI ID=0, which is the default ID of most internal HD's. The Mac will then search the SCSI chain in ascending order till it finds a drive in which it can boot from (I ripped this off from the old 68KMLA site!).
You could plug the Zip into your 6100 + blank disk, boot up off floppy and install Mac OS this way. I'm pretty sure that a DB25 parallel printer cable is not the same as a SCSI cable; even if the pinouts were the same SCSI cables have much better shielding and thicker gauge wire. And lastly, yes switch the Zip drive to terminated as it is on the end of the SCSI chain (in this case, on it's own but still "the end").
JB
You could plug the Zip into your 6100 + blank disk, boot up off floppy and install Mac OS this way. I'm pretty sure that a DB25 parallel printer cable is not the same as a SCSI cable; even if the pinouts were the same SCSI cables have much better shielding and thicker gauge wire. And lastly, yes switch the Zip drive to terminated as it is on the end of the SCSI chain (in this case, on it's own but still "the end").
JB