I see that the IC bus, apparently run by the German or Swiss railways or both, is over an hour quicker than the train, which takes a less direct much slower route.

Q- when is Germany going to do a high-speed rail line to Zurich from Munich? Seems a natural.

The IC bus is nice and comfortable. And in 2nd class on the upper deck you also have a better view than from the train.
The route of bus and train is somewhat the same.
It has free WiFi, good legroom and does not feel more crowded than a 2nd class car of a train.

I guess there will never be a high-speed rail line from Munich to Zurich as there is not much demand.
It's a fairly short drive (even by European standards) by car on freeways that are rarely crowded.
Zurich is a financial center, so you have more travels from/to other financial centers like London, Frankfurt or New York. And everyone traveling from there will fly anyway.

There are 2 companies running Zurich - Munich buses: https://meinfernbus.de/ (the cheaper one) and DB.

Just one reminder:

The buses leave from "Carpark Sihlquai" - which is close to the central railway station.
But Carpark means coach park, not a parking lot for automobiles.

There are 2 companies running Zurich - Munich buses.

DB runs the IC bus with fares as low as 19 euros - the other company is even cheaper?

Meinfernbus fares start at 15 EUR and those of DB at 19 EUR
http://www.checkmybus.ch/

On the site Menifernbus neckervd gives it says there is no Munich to Prague route available - I wonder how long this bus takes - IC bus is faster than trains - how about this Czech bus?

I entered München and Praha and got at least 1 bus every hr, a mix of Meinfernbus, DB-Bus, Deinbus, Eurolines Germany, Eurolines Suisse, Student Agency.
Meinfernbus is the cheapest one: 19 EUR

Meinfernbus fares start at 15 EUR
Meinfernbus is the cheapest one: 19 EUR>

????
I wanted to see which bus was quickest and could not easily find it - do you know - IC bus is faster than the train - how about the other ones?

cheers!

Zurich - Munich:
Train: 4 hrs 19 min
Bus DB: 3 hrs 43 min
meinfernbus:
direct: 3 hrs 45 min
with stops at Konstanz (cheaper for Swiss Travel Pass holders) and Friedrichshafen: 4 hrs 45 min
Expressbus: 4 hrs 05 min
Student Agency (Prague - Geneva bus), with stop at St. Gallen: 4 hrs 25 min

Hey it looks like I never responded and thanked everyone for their posts. Sorry I got lost in preparation.....

We ended up taking that train and it was very nice and convenient.

Better late than never - thanks for the thanks -yes trains are so so nice and all -buses are OK but trains always more comfy - well worth extra cost.