If you look the model/part number of that thermostat you're looking for on the internet, you should be able to find a PDF file of the owners manual to look at the wire diagrams and it will also let you know if the thermostat is compatible with your current set up with the oil heating and central a/c w/3 zones. RC & RH should be explained in the thermostat manual if the new thermostat wiring has been reconfigured to accommodate your setup. Hope this helps.