adding a wi fi stat to an existing trolatemp forced air zoning system

Basically you just can't do it. You will need to replace the zone control with something modern.  That control has one thermostat as the "master" zone. Its the only zone that can switch the system from heating to cooling. That thermostat uses both the O and B terminals to do so. The "slave" zone uses less wires. I was never a fan of this setup.  

A new zone control board from a manufacturer such as EWC or Honeywell will allow for better,  more reliable operation of the system.  You might be able to re-use the same motorized duct dampers, but I would update those as well if possible.