Unless you get any other suggestions... I would suggest making contact with Skyguide (Swiss ATC provider) since they will be able to point you in the right direction. They have an efficient
PR department so if they can't help you then they will certainly point you in the right direction.
Try
[email protected] !
That address will take you to the
PR department for Zurich ATC. They are very happy to help flight crews with questions or queries. I arranged a visit to ATC there for a colleague and myself and the request was dealt with very promptly.