Hello Hobie1
Thank you for your query.
You have a free storage on the day of arrival and the following four days. Every subsequent day costs CHF 5. Unfortunately we do not have an exact regulation how long the luggage stays at the station. Please inform the employee in Zurich when you will pick up your luggage in Zermatt. So that we can make a note of this on your luggage order.
I wish you a pleasant stay in Switzerland.
Greetings,
FatimaH