Best train

You don't really need a tour: the train/bus network is easy to navigate.

Zürich is not very close to the high Alps, unfortunately.
Accordingly, my pick would be Rigi, accessed by mountain railway from Arth-Goldau - itself an easy train ride away from Zürich.
There are several viewpoints and scenic areas on Rigi: I would start with Rigi Kulm at the very top, then head to the Känzeli viewpoint a bit further west (you can take the train again part of the way).

Stoos, with the Fronalpstock viewpoint, is also not too far: train to Schwytz, then bus to the Stoos funicular.

If you absolutely want higher mountains, then Titlis (in Engelberg) is the most reasonable option from Zürich.

An out of the usual trip suggestion: take a train on the old Gotthard route and get out at Göschenen, just before entering the old Gotthard tunnel. In the tiny square in front of the station a cogwheel train will be waiting to ferry passengers through a steep gorge to Andermatt, a quintessentially Swiss village crowned by mountains. At this step you are two hours by train from Zurich so it could be enough and you could just go back after a stroll. An extension could be taking another train to the Oberalp pass; there is actually little to do at the pass but stopping at the hotel/restaurant, but the ascent (and the the descent back to Andermatt) feels like taking off/landing on a plane; but it is not a plane, it is a train. Then go back to Andermatt and Zurich. (A further extension could be doing the round trip to Disentis, Chur and Zurich, but it would be several hours on trains).

Good weather necessary for this trip, and also bring a sweater as you would be going to very high elevation. Don't stop at Oberalp in winter, as the snow wall could be higher than the train....

Thanks for the suggestions!