When the ecu on my 2018 model r1200gsa needed replacement the new one had to be fully programmed at the factory including the one off factory written update that was unique for my bike to retain computer assist pro functions on a Basic model.
It might mean your secondhand ZFE unit may need to be reprogrammed if one or more options on it is different from on your original unit
It might mean your secondhand ZFE unit may need to be reprogrammed if one or more options on it is different from on your original unit