I can't find my ZCash z-address & my address keeps changing! Also, can I receiving ZEC mining rewards in Jaxx?

We only support transparent addresses at this time. We haven't made a full decision on supporting z-addresses yet. 

The address changing is normal. Jaxx is an HD (hierarchical deterministic) wallet, which means it generates a new address every time you send/receive funds to/from your Jaxx wallet as a way of keeping your balance private. And yes, you can use any of your previous addresses to receive funds.

And please do not point your ZEC mining rewards to Jaxx, as we are a lightweight wallet that is not designed to receive mining payouts. We do not recommend pointing any mining rig payouts to Jaxx as it may cause issues on your end as well as potentially causing issues on our end.