There are two options for internet access on site at UZH (the following text is copied from https://www.zi.uzh.ch/en/getting-started/guest.html):
Most universities and research institutions use eduroam. Members of such institutions have Internet access in the public areas of UZH via the eduroam WLAN network. We recommend testing eduroam access at your home university in advance to ensure that the configuration is correct.
As a guest at UZH, you can access the Internet everywhere where there is WLAN access: Simply select the uzh-guest WLAN network. After doing so, accept the Terms of Service and fill in the registration form with your mobile phone number. You will subsequently receive an access code by text message, which allows you to unlock Internet access. This option is available for all cell phone carriers that allow the receiving of SMS in Switzerland.