Yes, that's an annoyingly common power adapter connector. I don't know why anybody who chose it went for it instead of a normal barrel plug.
I have or have had a handful of devices that use it, but I'm not confident that any of them share a pin-out, so I use labelmaker or a silver sharpie to differentiate between the ones for my different devices.
To be honest, unless you're going for a specific look, or you find one that's complete and it has drivers, etc, I don't know if I'd bother looking for a ZipCD or any of Iomega's subsequent CD products. You can find external optical drives that are as good or better.
For PPC Macs, an external Firewire drive would be much better, for example, and for Intel Macs, whatever's on the shelf at your local Best Buy or Office Depot is going to work well enough, and likely newer. I mentioned this elsewhere, as well, but at least in 10.7+, blu-ray readers and writers should work for data discs. I haven't tried in 10.6 or older, though.