So they installed this single zone thermostat and wired both control board 12 volts lines to one thermostat.
https://cdn.ltvdns.com/leisurevans.c...Thermostat.pdf
I don’t see why you could not upgrade to CCC2 multi zone thermostat and replace that single control unit with multi zone and wire control wires accordingly for each unit.
It would beat option of trying to install another single zone thermostat for other unit and fish the wires
I also wonder if your unit has TWO remote room temperature sensors mounted? One in bedroom and other in living room areas
If not then you have two issues to deal with... and if RV don’t have the two separate remote temp sensors this explains why they installed a single zone thermostat.