EWC -ST-2D Zone 2 wiring

[angelop123]

My zone 1 thermostat has W Y RH/RC O B G C wiring
My Zone 2 has W Y R, no C (working fine with a battery operated thermostat)

If I add a C wire to my zone 2, I can use thermostats such as Ecobee.
My question: will it work even though it has no O or B wire? I will leave my zone 1 thermostat installed as is. I assume the zone one thermostat will take care of whatever the O and B are used for as it's doing now.

My controller is EWC-ST-2D

[Paul Z.]

Call 18004463110X490 and I will explain.