The Lindt factory tour requires a reservation/ticket for a specific time, so you have to coordinate that with your expected arrival time to Zurich and how long you estimate to get through passport control, check your luggage and get a train to the factory (about 90 minutes round trip). A guided tour is 90 minutes at specific times although you can just get tickets and do your own tour. You might need to buy this soon because they do sell out daily.
https://www.lindt-home-of-chocolate.com/en/
Another option is just touring around Zurich. An exceptional city with many great shops, old town, restaurants, some museums, etc. If the weather is good a boat ride on the lake is nice as well.
Keep in mind your time needed to get on to your next flight and the requirements needed. Nine hours sounds like a lot of time, but air travel always takes up a lot of it deplaning and boarding again. Enjoy your brief stay in Switzerland.