Curious to hear how you get on.
The 565 Z3 7.1 was my first Meridian piece and intro to Meridian. I never got serial to work with the config program and as others said, the legacy config program came after the 565, so from the earlier 861s and 568s onward.
I bet you might have success feeding it commands from an older computer with a native serial port. As I don't think a USB to serial cable with the built in adapter chip would work but don't quote me on that. It works for products that use the config program, just that from experience on products from that era pushing firmware. Like the old ML Proceed line or the old ADA stuff.
Manual on the 565 was really good though. It explained everything in great detail for the setup on the unit and resetting etc.
Meridian kept the same letter coded conventions for speaker/size layout and I always found referring back to the 565 manual helpful as a reminder to explain what each type was again.
Good luck.