I'm of two minds about your new itinerary. It is very good as is, but you might want to get a little bit more than half a day in Luzern.-
It is a really good idea to spend more than one day in the Jungfrau region. That allows extra time in case the weather is too cloudy to enjoy the area, so that you might have a contingency plan. I might visit Bern, for example as one contingency....about a 1 hour frequent train ride from Interlaken.
2.- Luzern is a wonderful place as well. So, I'd maybe stretch your time there a little bit, and travel to Interlaken and, for example, Wengen, in the mid afternoon. If it fits, a lake boat ride on Lake Lucerne is really nice, but the best part ( the southern end) is perhaps out of reach for you. ( see my photos in the following link, toward the end.)
I'd also adjust the Luzern to Interlaken transition if the weather in the Jungfrau region is really bad or Note however, that Swiss weather is full of microclimates due to the mountains, and I've seen thick fog and clouds in the AM turn almost instantly into sunshine...or, vice versa. That can be dramatic near the Jungfrau, and als, can be different up high from down in the valleys.
Attached screen grab done for someone else shows typical Luzern to Lauterrbrunnen trains. The Luzern -Interlaken express is that portion of the Golden pass route.
Local train stations, tourist offices and hotel receptions can help on that. There may be webcams in train stations at tourist offices, for example.
Since you'll not be jet-lagged from your short flight, you should be able to enjoy a good part of Day 1 and 1/2 to 2/3 of day 2 in and around Luzern.
Not sure when you get into Zürich Flughafen.
It is a fast airport for Schengen passports; you might not even have to go through passport control, since you arrive from a Schengen country.
You'll have your luggage quickly, and the train station is just across the street. Free luggage carts available in the Arrivals bgage claim area go up and down escalators (don't pile your luggage on too high...it might tip off on the escalators) , and there are what we in these former colonies call elevators, known as lifts in the UK, ;-) . With hand luggage, I've made it to the train on flights from Amsterdam in well under 30 minutes - even 20 minutes -from the time the plane door opened. Depends on where your plane stops and parks.
Please use the time table for train travel.
There are two trains per hour from the airport to Luzern. One goes through Zürich with no change of trains- departs at xx47. The other has a change of trains at Zürich, departs at xx18. Those come in on a lower level at track 32, usually, and the connection to tracks on the main level (for Luzern...tracks 3-18) might be tight. If so, there are other services to Luzern, and you can always wait for the next train coming through a half hour later ...the one that left Zürich Flughafen at xx47.