I have 2 MTH Z-1000's and just checked the output voltages, I got the same voltage on both the accessory and variable commons to positive terminals, regardless which common I used I got the same voltage at each positive. I would say yes to using the Z-1000's accessory output hot to the 022 constant voltage plug as it seems to make no difference in voltage. FYI; I was using a digital volt meter.
I have not tried this with my Z-1000, so I am not 100% sure if it will work, have only tested output voltages with my multimeter and have not tried it under an electrical load.
Lee Fritz