I'm a chemist, so I use chemists shorthand for mercury and the symbol for the element, which is Hg, from the Latin Hydrargum.
frHG is easier to type.....;-)
Annika has given good advice. Luzern is a very good place at which to begin.
I'd take the train from the airport directly to Luzern....two per hour, approx 1 hr trip, depending on whether you have to change at Zürich main station. You'll have time to walk around, see some of the famous sights.....
The timetable and a map will be helpful:
I'd stay the night of the 26th and spend the 27th in or around Luzern. I'd take the train to the Jungfrau region on the night of the 27th or the morning of the 28th. If you go in the morning, you'll see the sights. The scenic route via Meiringen, can be selected in the timetable; otherwise, the faster route via Bern will be selected automatically by the timetable software.Adjust that time as you please. From your comments, I cannot tell exactly when you must leave... perhaps the 30th, from some Swiss city? The Black Forest is not that far away.
I'd stay at one of Wengen, Grindelwalld, Mürren, with Lauterbrunnen a good alternative on the valley floor. Interlaken is more of a transfer point than a destination for sightseeing.
You can take the cograil train from Lauterbrunnen, Wengen, or Grindelwald to Kleine Scheidegg. Great scenery. At KS, the line has a branch (quite expensive) up to Jungfraujoch.
Many of the "ski" lifts in the region will not be running until approx. December 15th. Hotels may be closed until then as well. At the time of your trip, it s a few weeks before the ski season really starts, so alpine resorts are often closed for maintenance, repairs, and getting ready for the Christmas rush. Luzern is wide open.
You can do a little looking at webcams to see how much snow there is....by the end of November, there will be quite a bit at higher altitudes. The major mountain pass roads shut down for the winter due to snow depth in the first week or so of December.
www.myswitzerland.com/ en-us/service-aktuelles/webcams.html ?lc=de&cc=
Google for other webcam sites.
Trains run, mostly, so that you can count on them while you are there, even if there is snow.