I'd be very interested to see which Zero model will pull me (also > 100kg) up the kind of hills we have around our place. I wonder if I can test ride one up College Hill or Victoria St as they are right by the shop.
Why not give pop in or give them a call? At least you have the advantage of being in the same city! I'd like to have taken one for a test ride, but am not too worried I couldn't as I live in a flat city, and I know for sure the 10 will be better up slopes then my Xiaomi.
Interestingly the 9 and 10 have the same weight recommendations (120kg, I think), with the 8 lower and the 10X higher, but hills may well may a decent difference so trying one in the flesh is surely your best bet.