May I suggest the following:
stay in Lauterbrunnen Day 3, 4,5 - this will allow you enough time to go up to the Jungfrau, to the Schilthorn and to allow for bad weather.
Day6 - take the train from lauterbrunnen to montreaux. You can do the golden pass Route and enjoy the scenery. If you get an early train (I think around 10-11), you will arrive early afternoon which will give you enough time to sightsee.
Day 7 Zurich.
Not if you are leaving from Zurich or want to sight see.
We did the above but instead of staying in Montreaux we returned to Lauterbrunnen so we had no luggage - but we didn't want to shop -
If you have your heart set on seeing the Matterhorn - you could eliminate Lauterbrunnen and concentrate on Zermatt. We decided to skip the matterhorn and loved the Bernese Oberland area. Put in a plug for Hotel Jungfrau in Lauterbrunnen. They were great.
Enjoy