Swiss Saver Pass or Swiss Half Fare Card

Hello Francisco, and welcome! My first thought is that a 4 day Swiss Saver Flexi Pass would be a good option. You can use free travel days for the transfers Zurich Airport-Lucerne, Interlaken-Zermatt, Zermatt-St. Moritz and St. Moritz-Zurich. On the days in between, you will profit from a 50% discount for your shorter regional trips (25% for the Jungfraujoch). Calculations based on your plans would have to prove whether this is the cheapest solution, but it does seem to fit your plans. Details, including downloadable validity map, can be found through the Swiss Flexi Pass page. For a good comparison you may also want to visit the Swiss Half Fare Card and the Swiss Pass page.