You can buy a one-way ticket from London to Zurich on KLM. You can spend a whole day in Amsterdam this way: just as an example: 6:30 KL1000 to AMS, arrival 9:00. Spend the day in Amsterdam, fly in the evening on KL1969 to Zurich at 21:00, arrival in ZRH 22:25. The city center of Amsterdam is a 20 mins trainride away from the airport or a 30 mins busride. And Amsterdam is just small enough to do in a day. Walking the city centre, taking a canal cruise, have a nice lunch somewhere. The fare for your ticket is around EUR 175, check your possibilities on KLM.com or via google flights.So my vote goes to....Amsterdam!