I can't seem to find a reliable LH definition of a "Stopover" for locations in Europe.

I'm flying a LHR-FRA-SIN-SYD route and back on a Z fare. (ZRFGGB). As luck would have it (I hope), I now have a meeting in MUC on the day that I fly back, and the fare rules seem to suggest that SYD-SIN-FRA-MUC-LHR is an allowed routing.

Problem is, Stopovers are only allowed in Zone 3. I don't know whether or not a 9 hour break between arrival and departure in Munich would be considered a stopover or not? (Arrive 09:00, depart 18:00).

Can anyone point me in the direction of information that might clarify that? Thanks.