This is done at your own risk! Installation of internal drives of any sort is not officially endorsed by Akai EMI. Doing this may void your warranty.
Installing a Zip100 or Zip250 is relative straightforward and simple. Either ATAPI or SCSI will work. ATAPI will be easier to find and I imagine a bit cheaper. Also, when an ATAPI Zip is installed, replacing the floppy, the floppy controller gets disabled by the system and the MPC doesn't search for it, which is a good thing since it isn't there anymore. When SCSI used, the floppy controller is not disabled even though the floppy is not longer there and when you go to open or save the MPC tries to search for the floppy and just returns an error. It doesn't hurt anything but just annoying, so ATAPI is probably the preferred one to use. Also the an ATAPI Zip needs to be configured as MASTER.
The power cable that connects the floppy to the main board is very short and probably will not reach when you install the Zip drive. If you install an ATAPI Zip, you may have to cut the cable to install the proper connection since it is different. If SCSI, then the cable is not long enough, so you may have to cut into that one anyway.
You will have to modify the floppy's power supply cable in order to power any type of Zip drive so if you are uncomfortable with cutting wires, get a friend. No snipping alone! It is crucial that you do not destroy the white power connector end that attaches to the mainboard. I have not been able to find a supply of these types of connectors. If I did, I'd make the cables myself and mail them out to you!
Here's a pic of the power cable I am using. It's sort of bastardized at the moment since it started with two small connectors (one for internal HD and the other for the internal SCSI Zip. I recently changed one end for an internal ATAPI Zip drive and placed it in the MPC. For mine I only needed the +5V and the ground as shown below. I have heard from others some (maybe older) ATAPI Zips needed the 12V supply also. I don't know way to tell right off if you need the 12V. If for some reason your Zip does not work with just the 5V then you may need it. There is a 12V supply on the board that is part of the current connector and the leftmost pin of the 4 pin set if looking at it from the front.
Common things to check if you are having problems:
1. If the Zip drive doesn't appear to be working, try installing it in a computer to make sure it works.
2. Make sure the ribbon cables are turned the right direction. It's not readily obvious which direction they go, but if the MPC fails to boot, try switching the cable.
3. Make sure the the ribbon cable is firmly seated in the mainboard connector.
4. If the Zip drive light does not come on, it's usually a sign a power supply problem. Make sure the Zip is powered from the 5V connector.
5. The MPC should automatically detect the ATAPI device and replace FLOPPY with ATAPI in the Load and Save screens. If not there is a problem.
6. If you have more ideas, let me know.