OK, from what I remember back in the zip disk swapping days was that Amigas and Macs can format a dual partition disk. My Mac friend would give me a zip disk full of files and try to be a smart-ass by making two partitions: one Mac and the other PC. I was able to read both. But only the PC partition shows up on the PC.
So I returned the newly formatted zip disk to my Mac friend, but with three
partitions: PC, Mac and Amiga. Needless to say, he couldn't read the Amiga partition.