ZC's were older D-series engines, there were both SOHC and DOHC versions, I believe all pre-OBD (so pre '91 and older civics). If your running a P28 ECU, that's for a SOHC VTEC D16Z6 engine and if the check engine light is one, it's probably becuase the ECU can't see any of the VTEC equipment on the non-VTEC ZC engine. I would check the code and there might be other issues. I think 21 and 22 are the VTEC codes but there may be other sensors missing on the pre-OBD ZC engine that the OBD I ECU is looking for. Is the car driveable?