as you all know, Switzerland belong to the DACH market section and it is usually mailed with German messaging.
Not everyone is happy anyway about receiving only German communication and there are many international company that wish to receive information in French or English.
How do you overcome this obstacle? I was thinking about adding to the preference center a field with "Preferred Language of Communication".. Otherwise based on ZIP code, set up an operational campaign that assign preferred language.. but sometimes due to the internationalisation, this is not enough.
Any suggestions on best practice or how better implement segmentation for this country?
The zip code method you mentioned seemed like the best option possible. If you back it up with preferred language from another source and in your campaign specify that zip code language takes precedence if language from both sources are different, then you should be nearer to the leads actual language.