If you are visiting UZH as a researcher while on leave from your home institution, you will most likely be here as visiting scholar (visa status: academic guest).
The institutes/clinics are responsible for selecting and issuing an invitation. The inviting institutes/clinics also provide the infrastructure (workplace, e-mail, telephone, keys, UZH guest card, etc.).
The necessary entry and residence documents are organized by the visiting scholars themselves or by the inviting institutes/clinics.
Further information on relocation can be found here:
Relocation to Switzerland