Is your oil boiler currently controlled by 4 different thermostats, one for each zone, located at different places in your house? If so then yes you will need a Nest thermostat per zone to replace each of your thermostats. You should not need a C wire for the Nest 2nd or 3rd generation, I have not test the E or 2020 without a C wire.
My system is 3 zone valves older system with no circuit board to attach Honeywell RA832A. I understand that i will nee (3) Nest to control . I cant figure where to hook up C wire furnace. There is a transformer on the 832A? or do I have to pull power from zone valve. or is the C wire being used as a ground? thanks again new to this