we are renting a car for a week in january beginning/ending in zurich and would appreciate must do stops - how about munich/salzburg/vienna/innsbruck/gimmelwald? too aggressive?
Are you serious? You want to do six cities in seven days in the dead of winter? By driving? Half that would be too aggressive. You really need to consult a map and especially the mileage distance between those points Munich, Salzburg, and Vienna would be challenging even if you flew open jaw into Munich out of Vienna. You need to restart the planning with some good guide books and a map.
Not a chance at that time of year. Maybe Zurich to Munich and back, but that's about all you will be able to manage in one week in the winter and see more than the side of the road... well, maybe you could fit in Salzburg or Innsbruck, but not both. Skip Gimmelwald unless you want to go skiing... in which case, you would be better of staying in Murren.
Completely agree with the two previous posters. WAY too much. Consider a smaller loop starting northwest - Colmar, quaint villages and towns in the Alsace region, Strasbourg. Then turn east towards Munich and loop back maybe hitting Augsburg on the way. Forget going as far as Vienna. That's a 4-5 hour drive from Munich in good weather.