Part numbers roll over after a number of years.
For example:
For the Z3200 that the model # ends in a “B”; example Q6721B
The COMBO part (main pca + power supply) Q6719-67009 rolled to Q6719-67013
For just the power supply: Q6718-67005 rolled to Q6718-67033
Main pca piece can’t be ordered as a single part
For the Z3200 that ends in an “A”:
Combo part (main pca + PSU) Q6718-67029 rolled to Q6718-67034
Power supply same as above
So it's important to check to see if part numbers have rolled over to new numbers.
It is true that the print mech board must pair with the HD and the formatter.
While the manual suggests Service Menu Diagnostics, I have yet to see an HP Field Technician do this, and I haven't done it either since the first time. It won't hurt, but it ends up being a waste of time mostly.
I've observed, best practice is to install the replacement part, start up, then shut down (even though the printer most likely will not initialize) and replace the next, etc., etc.
One thing I've noticed is that these days it is much more difficult to get the printers running compared to 5 or more years ago.
I question why this is, but prefer to keep my thoughts to myself.
I have also observed that continual starting then shut down multiple times oddly has a positive effect and can sometimes bring a machine back online. (Operational that is).
While replacing parts seems like the correct thing to do, sometimes cables are the culprit, especially the one that runs from the print mech to the formatter. There is a phenomenon called TMI (too many insertions) that can happen when unplugging and replugging cables, or a cable can be inadvertently pinched when reassembling the printer.
Seating, inspecting and carefully reseating is a good practice but when it's done may times over, TMI can occur.
Best,
Mark