If it helps…??
The steering wheel controls work on resistance.
So many ohms for up, so many for down, left and right etc. (are these standard measurements between different cars, models, manufacturers… I don’t know)
I’m aware that with the chinese android units you have to teach them.
Basically, you would operate the steering wheel controls and confirm on the unit, what you just pressed.
If the JVC unit works the same, then I can’t see it being an issue.
I posted a thread some time back showing which two pins on the wiring loom are the ones for the steering wheel controls.
I confirmed these by measuring with a multi meter.
I’d imagine that the JVC will have an ISO wiring connection, so you’d need a Mazda to Iso converter, and that space is limited behind the unit.
Also, I’ve not seen an ISO converter with the steering wheel pins wired in, so you may have to wire these seperately.
It’s not an impossible task to fit another unit, but it’s not a straight swap.