The manual is really not so well worded about this. However, the implication is that you should not try to insert or remove the ZIP while the keyboard is off (not that you could do it anyways).
I leave the ZIP cartridge in the drive all the time, except when I want to make a backup or add stuff to it.
I did have a problem with the ZIP not being able to read, but I don't know if it is because I keep the disk in the drive, or despite of it. It worked fine by the way with a new cartridge.
I hope this helps.
Regards,
Alex
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Regards,
Alex