Zurich to Lauterbrunnen and then later Lauterbrunnen to Garmisch or Munich by Train or Bus

www.sbb.com will give you prices and times. Careful, the first price you see on the train list assumes you have a Half Fare Card, so double the price to get what you actually pay. Also, compare the price for a Swiss Card for 199 chf, that gives you your ticket from Zurich (assume airport) to Lautertbrunnen and your departure ticket from Lauterbrunnen to the Swiss border on the way to Munich/Garmisch, and half fare privliges while in Lauterbrunnen.
www.bahn.com gives prices and schedules for German trains.

Hi, we just did the first portion of your question: Zurich airport to Wengen (town up the mountain from Lauterbrunnen) Was 85 Swiss francs. The train station is underneath the airport so very handy. We arrived in Zurich at 10:30am and were on the 11:40 train, arriving in Lauterbrunnen at 2:45 and Wengen at 2:51pm. You change trains quickly at Bern and Interlaken Ost ( don't get off at Interlaken West!). Love their train system, and the ticket agent at the airport gave us the itinerary with each train line to switch at each station, too. Easy!

From Zurich to Lauterbrunnen both the train and car have a couple of routes to choose from, either via Bern or Luzern. The Bern route is relatively flat and relatively fast. The Luzern route is via the Brunig pass and somewhat slower.

I haven't timed it out but having done both routes both ways I would say that the Bern route is about the same time end to end, and if comparing the Brunig Pass route the car will be slightly faster because in the car you won't stop nearly so many times and you don't have to change ends at Meiringen like the train does. That being said when I was driving the Brunig pass this summer I got stuck behind a very very slow Spanish tour bus and there was nowhere to pass for nearly an hour. That road winds back and forth and round and round, even a spiral tunnel, and is only one lane each way with a solid white line down the middle.

Traffic in Zurich can be interesting, and I'm not a great fan of Zurich traffic. From the airport you may be able to avoid some of the traffic.

Parking in Lauterbrunnen is at a multi-story car park near the station. It is more expensive in winter - CHF 14 weekdays, CHF 17 weekends - than in summer, CHF 10 per day.

The train via Luzern and Brunig is exceptionally scenic.

I just realized that your thread title asks about train vs bus but your question is car vs train, which is what I responded to.

Are you interested in doing the trips by bus?

Re the onward journey to Munich or Garmisch-Partenkirchen.
Retrace the same route back to Zürich (but to "Zürich HB", the main station, NOT Zürich Flughafen). There are a few through trains per day from Zürich HB to Munich (München Hbf). See sbb.ch or bahn.de for details.
To get to Garmisch-Partenkirchen (to give it the full name), according to bahn.de the quickest route is Zürich HB to Innsbruck Hbf and then Innsbruck Hbf to Garmisch-Partenkirchen.