scenic train ride through the Mountains

Starting from where? Or ending where?

Zurich towards France

You don't specify which part of France, but I will assume you mean the Strasbourg/Paris side rather than the Lyon/Grenoble side closer to Geneva. There aren't really any mountains on the direct route from Zurich to France (via Basel). If you want to actually ride through mountain scenery, probably the best bet would be to make a pretty big detour south towards Luzern, then on to Interlaken, Bern and eventually end in Basel. This would take about 5 hours with 2 changes (Luzern and Interlaken). Doable but somewhat time-consuming depending on your final destination.

if you exit Switzerland through Lausanne or Geneva you could take a train to Brig and then turn right along the river valley; or perhaps Zurich - Bern - Spiez - Montreux - Lausanne/Geneva. The Spiez - Montreux is very scenic.

The straight run from Zurich to Basel for the most direct route to Paris is all flatland.

Thank you for all the tips!