All here will say that's not enough days to see Switzerland, but I think it will show you that it's worth a longer visit in the future.
Geneva and Zurich are big cities, and not in the mountains that Switzerland is famous for. Geneva is, to me, a very nice city, on a beautiful lake, you can see mountains in the distance. Geneva is much closer than Zurich, and honestly, the last part of the train ride from Geneva to Zurich isn't all that beautiful.
So I'd take a train to Geneva, ideally to Cournavin station in the center of town, not to the Airport. if you left Paris Gare de Lyon at 10:34, you could be at Geneva at 14:35. From there I'd suggest putting your luggage in lockers, and walking down to the lake, it's a beautiful lake. You can see the famous Jet d'Eau (big fountain). Then back to either the train station and a short train ride to Montreaux. Or possibly a boat to Montreaux, that would be awesome if you could fit it in.
Montreaux is a beautiful town on the north shore of Lake Geneva. Lots of hotels, beautiful flowers on the lakeside promenade. Big statue of Freddie Mercury. You could stay there for one or two nights, visit Castle Chillon, then go on into the mountains, perhaps the Interlaken area. Then take a train to Zurich via Lucerne (beautiful scenery here), and continue on to Zurich and fly home. Very likely you'll find more flight choices out of Zurich and Geneva.
So many possibilities. I think to go from Paris to Interlaken or Lucerne might be too many hours in one day, Others will comment on that. And others will comment on Montreaux being too far away for the first night or not. I really think flying back from Zurich would show you a lot more Switzerland than flying back from Geneva. You could look up the Panorama Express train, if you could fit that in, it would be a very memorable, beautiful trip.
The Swiss train system is the best. Glad you are using the trains. There are Swiss Rail passes and half-fare cards that might fit your schedule. Others here will have suggestions about that.
You will really love seeing Switzerland, and want to come back!