Nowadays, many suppliers offer locomotive decoders for Z gauge.
However, the installation of these decoders is far apart from being easy:
Parts of the locomotive have to be removed, conductive strips must be isolated and wires have to be soldered on. Such modifications to a locomotive are serious and can hardly be switched back.
The consequence: Depreciation.
I looked for a solution to completely replace the printed circuit boards in the locomotives by custom-made locomotive decoders.
The modifications of a locomotive shoult not be more than:
Open the cover, unscrew and remove the circuit board, insert and fix the decoder, close the cover, finished.