This edit (and the one I made immediately before it) are based on changed published on the city website, where they announced the loosening of the restrictions on this section of Bahnhofstrasse: https://www.stadt-zuerich.ch/site/velo/de/index/erfolgreich-umgesetzt.html (and search for "Bahnhofstrasse (2. Massnahme)"). There is a chance I implemented the described change incorrectly, though. A picture of the sign is on the webpage.