Can you put a carnet of 10 tickets between RER zone 2(or higher) and first zone, or just the first zone carnet?
Navigo Easy can only hold Paris Metro tickets & carnets at the moment, not RER tickets with zones.
Navigo Easy can't hold RER tickets at all. And only RER tickets are subject to zones (or more precisely: specific stations). The Paris Metro network is considered a single zone.
The complication with RER tickets currently is their specific station-to-station nature. RER tickets literally show the origin and destination stations on the face of the ticket. And you can customize a RER ticket for any departure/arrival stations.
For the moment (2019/2020) the RATP doesn't have a solution for preloaded, station specific RER tickets on Navigo Easy. Paris Metro tickets are generic (they're all the same and don't specific particular stations) and debiting them from the Navigo Easy is simple.
So Navigo Easy can only load Paris Metro carnets, which are good/valid for Paris RER zone 1.