I use exactly the same setup. It's super easy and straightforward.
Set the Z-7 to omni mode -> choose the bank/location on Z-12 where you want to save the preset -> set the amp the way you want -> hold Write/Edit button on Z-7 for roughly 3 seconds (the red LED will flash and then stop) ... and you're good to go
Example: select location 01 -> select clean channel, Presence A, Master B and reverb active -> hold Write/Edit button and voila there you have your clean setting
select location 02 -> select lead channel, Presence A, Master A (everything else off) -> hold Write/Edit and there is your metal rhythm setting