@jon for me, the carte avantage and carte zou (région PACA) work together just fine. I have loads of other complaints about SNCF Connect but this isn't one of them.
It's even pretty good at working out which discounts/tariffs to use if I have multiple travellers with multiple cards (PACA does cheap group tickets).
My test journey is Nice <-> Paris via TER to Marseille then TGV inOui. It uses the Zou discount for the TER and the Carte Avantage for the TGV.