The WK flight arrives ZRH at 11:50am. Add the layover, 50 min ZRH-GVA, 30 min for baggage retrieval, waiting for the bus and then 1h30 for the bus itself.

I'd suggest to book the shorter connection as that will get you to Chamonix in the late afternoon, whereas the longer connection will put you in the rush hour traffic and the queue at the French border.