Swiss alps and Dolomites in one trip

You really need to get more specific.. I suggest you go to Google Maps first.

Either to Milan, then up to Bolzano/Meran.
Or, to Zernez, postal bus to Mals, train from Mals.

If by efficient you mean fast, rent a car. It won’t be cheap if you are picking it up in one country and dropping it off in another.

To find routes between cities using public transportation, google Lauterbrunnen to Ortesei to (for example) and click the train symbol.

I suggest you split this up into two trips. It's not that easy to travel from the Swiss Alps to the Italian side, no matter the means of transport.

use Rome2rio for a variety of options. also consider whether the one will be different enough from the other for the effort, youtube is full of travel vlogs.

All you are doing is rushing a round Europe to see more or less the same..... If you were going to see something very different it might be worth the effort, but not for more of the same. Pick one and send some decent amount of time getting to know the area. And it really does not matter which since both will be new to you. If you want more of the same then go to the other at a later stage.

Let us know what you mean by Swiss Alps. Bernese Overland/Lauterbrunnen or St Moritz or Matterhorn or ??
Assuming you mean BO near Interlaken then:
The best train option might be 8-9 hours once you get to Interlaken and only to get you to Kastleruth and the best car journey is 5.5 hours for the same thing.
Let us know if you can be convinced to make it all Italy or all Switzerland and if not let us know where in the Swiss Alps and if you have a preference for a car rental or train and I/we can give you some ideas.