Munich to Zurich in 8 days

You say you have a conference and you have 8 days, but how long is the conference?
Or, how many days do you really have to get from Munich at the end of the conference
to Zurich?

Salzburg is 2 hours by train from Munich. Zermatt is 4 hours by train by Zurich.
Garmisch and St Anton are more or less on the way from Munich to Zurich. I'd
say that as long you don't try to hit 3 or 4 places and have 4 or 5 days, you could
hit any of those places. It's not that much of a extension or a backtrack. Innsbruck
is an option also. Hallstadt, as overhyped as it is, is about 90 more minutes from
Salzburg.

Are you open to renting a car and driving, or are you wed to trains?

How many days will you be at the conference? Maybe husband and kids can do Salzburg while you slave away at your conference.

Sorry I should have said . . . after the conference I have 8 days to travel . . . 8 days to see/do before needing to be on my flight out of Zurich.

I am open to trains or car . . . what do you recommend in that region? AND what are in your opinion the not to be missed places . . . do any of them require a car?

Public xport is very good in that part of the world, but you have to be open to
figuring out how it works, especially (IMO) if you start wanting/needing to use
buses as opposed to trains.

I will say that if you rent a car in Germany and return it in Switzerland, you'll most
likely pay a possibly large dropoff charge. But with 8 days, you could do 2 places
pretty well, and not really have to go in a straight line to Zurich to do it.

If you have a free half day while in Munich, there is Dachau. I would definitely
consider Salzburg; the festival will just have ended and perhaps it won't be quite
so crowded. If you want mountains there are multiple options; Kitzbuhel, Zugspitze,
Wengen/Murren, Zermatt. Lucerne is worth a day or two.

I am not answering your "best bets" question because that's kind of in the eye of the
beholder, and to be honest, your list of preferences didn't really narrow it down all
that much. But you have a decent amount of time. I might go with one city (Salzburg)
and then one mountain town/village to get some variety.

If you rented a car in Germany, and dropped it in Switzerland , you would get hit with a big International drop charge, The car would have to be transported back to Germany, and you pay for that and then some.

If you’re interested in art history, you could choose a relatively direct route and split your time between Oberschwaben (the Upper Swabian Baroque Route: https://www.oberschwaben-tourismus.de/en/world-of-travel/upper-swabian-baroque-route#/article) and Lake Constance; if you have a rental car, something like this:

(1) Ulm (gothic cathedral, fishermen’s quarter) and Wiblingen (Baroque monastery library)

(2) Zwiefalten (Roccoco church) and Ochsenhausen (with the famous Gabler organ)

(3) Bad Schussenried (monastery library) and Weingarten (Germany’s largest Baroque basilica)

(4) Ravensburg (medieval town) and Meersburg (beautifully situated on and overlooking Lake Constance; excellent state winery with a tasting room and a magnificent viewing terrace)

(5) Konstanz and Mainau Island

(6) Birnau and Salem

(7) Lindau and Bregenz - from the Pfänder (accessible by cable car), there is a great view of the lake

Accommodations in Upper Swabia can be found on short notice through Booking etc. or local tourist offices; I'd look in one of the small spa towns, like Bad Wurzach or Bad Waldsee. At Lake Constance, it’s advisable to book in advance (my favorite location is Oberreitnau, north of Lindau, but there are, of course, many other options).

In this particular case, I would rent the car from Hertz and return it in Lindau, because the drop-off fee in Switzerland would be very high. Hertz has a location about 300 meters from the Lindau-Reutin train station, where the train to Zurich stops. The other rental companies are farther away, so you would have to arrange your own transportation to the station.

A key point to look at is prices, anything that involves people giving service in Switzerland is expensive. Whilst the Zurich part may be a business expense, and the Zurich flights will be priced to compete with other airports the rest is out of your pocket. And it's worse than that, especially for 4 people because in some border areas the prices have hit casual tourism meaning places have closed down. Luzern is stil trading -at Luzern prices. So with Zurich being so close to two other cheaper countries it makes sense to go and tour. But if you've already been in Zurich I would give Munich a miss, it's OK (even nicer) but still big city.

Innsbruck city is very easy from Zurich, but for activity there is also Innsbruck Land - the country areas around the city, the area is served by local train, bus and mountain tram from Innsbruck main station, direct trains from Zurich about every 2 hours, the 08:40 (train EC163) has a glass roofed panorama car in 1st class https://www.vagonweb.cz/fotogalerie/CH/SBB/Apm-pano?f=2026 , possibly for the final year. Opposite direction it's EC164 at 15:47 from Innsbruck - for reservations it's Car 311 in both directions.

Salzburg city (and Salzburg Land) are not a mad idea. From 10:40 the 2 hourly service from Zurich goes to Salzburg (and further) in less than 5½ hours, these trains are so comfortable it's not really worth paying for 1st class, this is 2nd class https://www.vagonweb.cz/fotogalerie/A/OeBB/Bmpz-2290-2-4?f=2026. Or - for a real alpine experience - use the panorama car and go beyond Innsbruck, stay a few nights in Zell am See https://www.zellamsee.at/en/ or just go through to Bischofshofen and change for the original route to Salzburg or a village like Werfen https://werfen.at/en/home-en with it's castle and adventure activities but still only 40 mins by train to Salzburg city for a day trip. Innsbruck city and Werfen would make a good combination.