Gardenmoen (OSL) has been my destination airport and return starting point airport but I have not connected at OSL. With that said, OSL is compact (i.e. one interconnected terminal, not multiple terminals). http://www.oslo-airport.com/
Oslo Airport has one unique terminal, which is 819 metres long. The
Terminal is divided in two piers (East and West). The domestic flights
are served in the east part (gates 2 to 26), and the international
flights from the west part (gates 35-59).
The Terminal is divided in two levels, Departures Level on the Ground
Floor and Arrivals Level at Level 1.
For OSL transfer advice see:
https://avinor.no/en/airport/practical-information/plan-your-trip/transfer/transfer
Coming from International bound for International
You can use the transfer point at gates E12/E13 on the arrivals level.
Follow "Transfer" signs.
Baggage must not be collected if it is checked through to the end
destination. This depends on the airline and type of ticket. Check
your luggage tag!
However, the "baggage must not be collected" only applies if your baggage is checked through to your final destination. Given that you appear to be traveling on two tickets, SAS to OSL then Norwegian from OSL, you will need to exit and pick up luggage from the SAS arrival then recheck your luggage through to your Norwegian Air destination. The transfer advice will not apply.
My experience is that 60 minutes is adequate for arrival through retrieving checked luggage including oversize bags and that 90 minutes is adequate for departure including checking in bags. The combined 2.5 hours should be adequate assuming that the flight from Zurich arrives substantially on time.
Given that you appear to already have tickets in hand, there is not much you can do other than be familiar with the airport layout and be prepared to move quickly. You may also want to find out from Norwegian Air options should you miss the ticketed flight.
