If the detectors are NO going closed in an alarm then to put them all on the same zone they will need to be wired in parallel.

If they are wired in parallel then you cannot put an EOL on each leg and expect it to work correctly. In fact there is no termination method that will work correctly in this scenario and each device should be placed on its own zone with its own EOL placed at the detector. You could put an EOL on one leg only and the circuit will work, but not all the cables will be correctly monitored for fault conditions, only the one you fitted the EOL on.

If the devices can be set to NC going open on alarm then they can be wired in series at the CP end and one EOL can be fitted, preferably at the end of the longest wire run.