Of course you can buy prepaid cards at the operators shops at Zuerich airport.
The Swisscom offer is true, you pay 0.80CHF for all "on-net" (natel-to-natel) calls up to 1 hour. If you plan to make long calls that's great. If you plan to make most shorter calls (<3min) it's better to go with Orangeclick which you should be able to buy at Orange shops. It's also very cheap to buy.
Anyway you can find all information on this website too, just
click here.
While in Munich I'd go with some of the "supermarket operators". The cheapest for on-net calls (1ct/min) should be
SMobil which you can find at any
Schlecker store at 9.90 euros with 10 of credit. It's usually very common to find Schlecker stores in big German cities.