Your Athearn example uses the DH123/143 series with the AT clip option, can the DZ123 be used for Athearn older diesels?
I am interested because of the small space in S2/4 models.
Is the 1 amp DZ123 an option I can use?
It is possible that the DZ123 could be used in the older Athearn switchers, but the most important issue will be how much electrical current that the locomotive requires.
If the locomotive's stall current is below 1 amp, then the DZ123 can be used.
Otherwise, the locomotive motor will eventually, sooner or later, destroy the decoder by drawing more electrical current than the decoder's amperage rating.
You may also find that the DN series decoders, although somewhat larger than the DZ series, may also be a solution, and some have higher amperage ratings.