SamusDrake wrote:... Another question is what other components would I need other than just a Pi and Z80 chip?....
You would need just about everything listed in the kit that Heater posted above.
Note the site mentions using a RPi Zero to get HDMI and USB.
Any interface to/from the RPi would need have level translate circuits. 3V3 to 5V
You could easily communicate from RPI to Z80 over serial 3 wires. (via UART on the Z80 board)
IMO it would be possible but not feasible to attempt to interface the RPi to D0-D7 and A0-A15 etc.
Unless specified otherwise my response is based on the latest and fully updated RPiOS Buster w/ Desktop OS.