Are you planning stops at smaller towns not mentioned here? Smaller towns provide a very different view of the culture and history of each area and are often cheaper, more walkable, more friendly, more architecturally and naturally beautiful, and less stressful. Your focus on big cities makes me think that you chose these names off a map and have not yet done much research. You haven't said when the trip will be, so perhaps you still have lots of time to fill in the details.
Rick summarizes lots of great smaller town destinations on this site at http://www.ricksteves.com/europe, and covers them in his TV shows, but most importantly, he provides detailed information in his guidebooks. The Best of Europe book is designed for this type of multi-country visit, but his coverage of Strasbourg (and the recommended town of Colmar), Marseille (and the recommended town of Cassis), Munich, Zurich, and Luzern are in other books. I would also drop Zurich in favor of the Berner Oberland and/or Luzern.