You can not have baseboard copper fin on the same thermostat or zone with cast iron. Base board transfers heat much faster therefore will sit cold while cast iron rads are hot for much longer time heating a room. Also it is not recommended to have baseboard heat even on its own thermostat and zone when you have other zones with cast iron. The average boiler temperature on a system with all cast iron is much lower than the average boiler temperature of a system with all baseboard, especially on days where it is not so cold.
On a 50 degree day your cast iron radiators and boiler will maintain close to the same temperature around 100 degrees to maintain 70 degrees in a room, on a 50 degree day your boiler temperature will be much higher on a system with all copper fin baseboard, this is because of the much faster heat transfer from copper fin, causing your boiler to cycle on and off much more frequently but at shorter durations then with cast iron. Your boiler temperature will stay much higher.
What happens now is when a zone with cast iron calls for heat the boiler gets flooded with much colder water causing excessive noise from your pipes from the huge temperature difference in the water, you will now create air in the system from Cold water meeting much hotter water very suddenly. Even with the proper air removal scoops and bleeders you should never have extreme differences in system temperatures.
I have 9 zones of heat in my home and they are all cast iron except for my kitchen witch is copper fin and has 3 exterior walls. The system does not function properly unless I leave the kitchen zone off completely. I am switching to cast iron baseboard which is very expensive but will work exactly like cast iron radiators. That is what I suggest you do.