Poottoodau98
Or just get a Zurich Airport - Kilchberg ZH return (24h) ticket. The result is the same, a ZVV 4 Zone 24h ticket for zones 110 (which counts as 2 zones), 121 and 150.
Its validity period ideally should start with the departure time of your train leaving the airport, the price is 18.40 full fare.
A look at the => ZVV zone plan maybe helps understanding. With that ticket you still can use any public transportation e.g. in Zurich City (zone 110) after the Lindt visit, until the ticket validity is expiring.