Help with 16 night itinerary for 2025 trip

A train from Zürich Flughafen (Zurich’s airport train station) to Luzern has a connection taking 1h 15m.
From Luzern to Lauterbrunnen there’s a transfer taking 2h 30m. From Lauterbrunnen station you’ll need to connect to get to Mürren (30m).
Traveling from Lauterbrunnen to Zermatt takes 2h 45m (three connections).
From Zermatt to Montreux takes 2h 45m with a transfer. There are direct trains from Montreux to Genève-Aéroport (1h 30m). Total time on trains is 11h 45m with eight transfers.
A train from Luzern to Zermatt takes 3h 15 with two connections. From Zermatt to Montreux takes 2h 45m with one transfer. From Montreux to Lauterbrunnen takes 3h with three transfers. A train from Lauterbrunnen to Zürich Flughafen takes 2h 45 with a minimum of two connections. Total time on trains takes 13h 30m with eleven transfers.

Either is fine. But some adjustments....

Into Zurich/Out of Geneva
Luzern 4 nights
Murren 6 nights
Zermatt 3 nights
Montreux 3 night - you can get to the airport from Montreux easily without moving to Geneva, so add that night to Luzern or Murren.

Or...

Into Zurich/Out of Zurich
Zermatt 3 nights
Montreux 3 nights
Golden Pass Express to Interlaken - on to Murren 6 nights
Luzern 4 nights - fly out from Zurich

A train from Zürich Flughafen (Zurich’s airport train station) to Luzern has a connection taking 1h 15m.
From Luzern to Lauterbrunnen there’s a transfer taking 2h 30m. From Lauterbrunnen station you’ll need to connect to get to Mürren (30m).....

Thanks MaryPat for calculating the times for each itinerary! Do you think it is worth the extra hour and 45 minutes of the second itinerary to ride the entire Golden Pass vs the shorter total time of the first, which would only include about half of the Golden Pass?

Either is fine. But some adjustments....

Thanks wanderweg for the suggestions! I think our idea for a night in Geneva was to reduce the drama that can be getting children to an airport. But if it is relatively easy I wouldn't mind staying another night in Montreux.

If you wish to ride the entire Golden Pass route, in the proper direction (heading toward Montreux for the gorgeous views of the lake as you come down from the pass), it makes sense to put Zermatt between Muerren and Montreux as you have in your original itinerary. That way you have Zermatt as a detour from the Golden Pass route starting and returning to Spiez.

Go one way to Zermatt with the fast train through the tunnel to Visp, and the other using the regional train via Kandersteg between Brig and Spiez. You can see these routes (and the tunnels) on this Swiss rail map, which as the Golden Pass and other scenic routs highlighted:

https://www.travelswitzerland.com/en/download/swiss-travel-system-map-en-2023/?wpdmdl=14294&masterkey=63a023c8da36c

We spent the night before flying out of Geneva in the smaller lakeside town of Morges, which I recall was only 30 minutes from the airport by train (with no changes on the way). Our hotel was right on the lakefront promenade, which made for a nice peaceful stroll after dinner.