>> Arr Zurich 25 Apr for 2 night stay.
Unless you have specific things you want to do in Zürich, consider staying just one night and add an extra night to Luzern/Lucerne, Interlaken/Jungfrau Region, Zermatt or St Moritz. All of those places have so much more to offer than Zürich has.
>> 27 Apr travel to Lucerne via St Gallen
I would go straight to Luzern from Zürich if you are not planning on spending any time in St Gallen. I have dim memories of the Voralpen Express route from St Gallen to Luzern, but I don’t think it is worth such a long detour. It certainly doesn’t compare with the other scenic routes. Other opinions may differ ;-) I don’t recall anything particularly special about the route from Zürich to St Gallen.
If you do go to Luzern via St Gallen, make sure to choose the Voralpen-Express to Luzern (shown as VAE in the Swiss Timetable). The trip will take about half-an-hour longer than going back through Zürich, but there will be fewer connections, and you will see different scenery.
>> 28 Apr return Day trip to Mt Titlis (train and cable car)
The gondolas will be operating. With only one day in the area, you do run the risk of the weather not being suitable for a mountain-top visit. Have a back-up plan so you are not left wondering what to do with yourself if the weather doesn’t cooperate :-)
>> 29 Apr Train Lucerne to Interlaken ( Gold Pass)
The train route from Luzern to Montreux is called the Golden Pass. You could consider getting off the train at Brienz and going the rest of the way to Interlaken Ost by boat. It’s an easy transfer, even with luggage – very short walk, no stairs. However, boat departures will be very limited in April, so you will need to plan carefully to connect with a boat at Brienz.
The villages in the Jungfrau Region (Wengen, Mürren, Grindelwald, Lauterbrunnen) offer so much more scenic beauty than Interlaken, so consider staying in one of those places instead of Interlaken.
You might have time to visit the beautiful village of Mürren if you arrive in the Jungfrau Region early enough.
>> 30 Apr return day trip to Jungfrau (cable car)
As Lucas mentioned, the trip to the Jungfraujoch is entirely by train. You can go up via Grindelwald and back via Wengen (or vice versa), as each route has magnificent, but different, scenery.
Again, with only one day in the area, you run the risk of the Jungfraujoch being in the clouds the day you want to visit, so have a back up plan for going somewhere else if necessary, so you can make the most of your limited time.
The following mountain transport will probably not be operating when you are there:
Grindelwald – First gondola
Grindelwald – Männlichen gondola
Wengen – Männlichen cable car
Mürren – Allmendhubel funicular
Wilderswil-Schynige Platte train
The funicular from Interlaken to Harder Kulm should be operating, as should the cable car from Mürren to the Schilthorn (which should reopen on 29 April after a maintenance closure between 24-28 April).
The cable car from Lauterbrunnen to Grütschalp is likely to be open on 29 April, but closed from 30 April until 4 May. On 30 April, Mürren will still be accessible via cable car from Stechelberg (and bus to Stechelberg from Lauterbrunnen station).
>> 1 May Train Interlaken to Montreux ... 2 May Montreux sightseeing
I presume you will be taking the Golden Pass route via Zweisimmen? The timetable will suggest faster routes via Bern unless you put "via Zweisimmen" into your timetable search.
This page might be useful if you haven’t already decided what to do in Montreux.
>> 3 May Train Montreux to Zermatt
If the weather for the following day looks dodgy for a mountain-top visit, and your arrival day is clear, I suggest you be prepared to go straight up to the Gornergrat, after depositing your luggage in the lockers at Zermatt station (down the stairs).
You can check conditions with the webcams:
Otherwise, you could do a village walk:
>> 4 May Return day trip to Matterhorn (Gornergrat Railway)
Check the weather and the webcam before going up, in case the Matterhorn is in the clouds. If you ended up going to the Gornergrat the previous day, you could go up to Klein Matterhorn/Glacier Paradise this day, or to one of the other vantage points if the weather is clear.
>> 5 May Train Zermatt to St Moritz. (Glacier Express) ... 6 May St Moritz sightseeing
Unfortunately nearly all the mountain transport in the area will be closed for maintenance when you are there, and a lot of the shops will also be closed.
The Corvatsch cable car from Surlej/Silvaplana will probably be operating, as will the cable car up to view the Diavolezza glacier. The Diavolezza cable car is not covered at all by the Swiss Travel Pass, but if your hotel provides the “mountain railways included” card, it will be free with that.
www.engadin.stmoritz.c h/sommer/en/bergbahnen -inclusive/
>> 7 May Train St Moritz to Lugano
The train only goes as far as Tirano, then you transfer to the Bernina Express bus. Reservations are compulsory for the Bernina Express - both the train and the bus.
>> 8 May Lugano sightseeing
Boats and funiculars will all operating.
>> 9 May Train Lugano to Zurich.
That is a Wednesday, so the Gotthard Panorama Express won’t be operating, but you can follow the same route in normal trains if you want to.
To get the Gotthard Panorama Express route in the timetable, you will need to do your timetable search in two stages:
1. Lugano to Flüelen: put “via Göschenen” into your timetable search to avoid the long Gotthard-Basistunnel.
2. Flüelen to Luzern: use advanced search and limit transport mode to “ship” if you want to do the final sector by boat. There will probably only be 4 boats for the day between Flüelen and Luzern, so first choose your boat, then select a train to connect with it.