I got my accomodation by asking my supervisor to ask around in the laboratory where I would work. I quickly got two offers and ended up getting a great deal on a room in a house very close to the laboratory. The standard of the accommodation was great and the cost was 400 CHF per month (this was a very cheap price due to that the landlady gave me a discount because I am a student). I was living together with two other people in a house so I shared bathroom and kitchen. However, I decided to also try another part of the city and moved to a new apartment shared with two students (also this through a contact at the lab), this room costed me 660 CHF per month. Due to that Zürich is quite small the accessibility to both campus and hospitals is generally good hence wherever you live you will manage to get around easily.
https://www.ethz.ch/en/studies/non-degree-courses/exchange-and-visiting-studies.html
(information from ETH Zurich for international students)
http://www.marktplatz.uzh.ch/
(student whiteboard for apartments and other things – unfortunately mostly in German)
https://www.homegate.ch/en
(the biggest real estate portal in Switzerland)