Ghovolett40
The ˋissue‘ related to possible discounts within regional fare networks is basically known, but maybe not by everyone.
The reason is that for a given itinerary, obviously only one ticket and not multiple tickets can be issued. Also, the involved zone ticket could not be valid anymore on a different later connection, if the first or last stop within the fare network happens to be in a different zone (e.g. IR/IC instead of S/R train).
The workaround is either to be aware of such price oddities if your journey starts or ends near the border of a fare network such as Z-Pass.
Or use EasyRide, where the tickets are calculated retrospectively and where splitting into cheaper tickets like in your example does work.