Two questions first, how long is your vacation and do you really want to see Munich?

I would suggest doing you trip in reverse and skiping Munich. You can take the ICE train from Frankfurt in Interlaken in 5 hours. Interlaken is beautiful and there are many things to see all around there. From there head south to Italy, enjoying the scenery on the way. You may want to stop off in Chamonix and enter Italy that way. It should be great in the summer. Head to Genoa and then on to the Cinque Terre. Over to Pisa, a stop in Florence, up to Venice. Then when your ready over to Verona and then on to Milan. That's it. Have a good trip.

Greg