Zammad does not provide any functionality that detects languages at any way - at least not communication wise. As far as I’m aware there’s usually no indicators (except the written text itself) that would allow to do so realible.
Usually customers workaround this issue by either having a custom attribute that indicates the users language (for triggers / filters) on the user or organization. Other approaches would be to filter by e.g. top level domains (e.g. .fr) which however may produce false positives.