The downloaded ZIP folder requires a password to be extracted. I can't seem to find it anywhere.
According to the official website, to obtain the ZIP password, you will have to contact Jan Seibert using the following email address: jan.seibert@geo.uzh.ch
jan.seibert@geo.uzh.ch
To know more about it, use the official website: http://www.geo.uzh.ch/en/units/h2k/services/hbv-model