I have just returned from a 16 day packed itinerary trip of Switzerland and i believe some days, you have too much planned and is not feasible. I will outline them below. You should be aware that it is very tiring having a packed itinerary and will need to be very disciplined in terms of timing as some trains runs only every hour. Also, you have not factored in bad weather days to have back up plans. My other advice is to always check weather forecast the day before and also in the morning before heading out and most importantly the live webcams. Even then, as anyone who has experience in the mountains can tell you that weather can change very quickly and nothing is guaranteed.
Day 1: Assuming you arrive noon or 1pm in Zurich , then yes, Day 1 is feasible but rushed. Not sure how much luggage you will have too. But possible to store them at the train station lockers. Rhinefalls is 1 hour away each way and factor in 1 hour to explore the falls. Lucerne is also 1 hour by train.
Day 2: Is not feasible to do all 3 Mt Titlis, Pilatus & Rigi. You have to choose only 2 and that is also rushed. Mt Titlis is out of Lucerne, at least an hour by train from Lucerne. Pilatus and Rigi is much closer. I did both Pilatus and Rigi but on separate days. It is possible to do both Pilatus and Rigi in one day. I did Pilatus early morning, catching the train from Lucerne to Alpnachstad, to take the cogwheel train up to Pilatus Kulm. I was done with sightseeing by 11 am at the top and back in Lucerne at 12. The cable car was closed due to strong winds, so had to go back down the same route with the cogwheel train.
Rigi would involve a boat cruise on Lake Lucerne, so you don't need to do the cruise in the evening. I was on Rigi and it was a very nice sunny day, but i could see that Pilatus peak was covered in clouds but below it was totally clear. So, those who went up to Pilatus could only see clouds.
Mt Titlis is unique as it has a 360 degree rotating cable car but as mentioned it is much further out of Lucerne. And assuming you have a Swiss Travel Pass, you get a 50% discount while for Pilatus and Rigi, both are completely free.
Day 3 & 4:
Trip to Jungfraujoch is a whole day affair and only to be done on a good weather day.
It takes just over 1.5 hours for the Lucerne - Interlaken express and another 35 minutes into Grindelwald. Wengen is on the other side of the mountain which you could go up to Maanlichen and down to Wengen from Grindelwald or go into Lauterbrunnen and up to Wengen which is free with the STP.
I would highly recommend the gondola to First and a short 40 min hike to Bachalpsee. If you have time, perhaps consider continuing to Faulhorn (2681m) another 1 to 1.5 hours, which i did.
Day 5: As suggested by Arno, check out the Golden pass line between Zweisimmen and Montreux, which has amazing views but takes longer than if you were to take the quickest route. Chillon castle would be the main goal in Montreux.