While Hotel Wellenberg is located on a noisy square, I wonder that Hotel Roessli should be noisy too. It's on a rather quiet side street, the only noise could come from its own bar which is a pretty small one or from people returning home. These two hotels are both very central with lots of boutiques and restaurants around.
Hotel Florhof is on a comparatively very quiet location (beside of the own restaurant terrace which could cause some noise too), just outside of old town. To reach the shops and restaurants it's only a few minutes walking. Or there is a bus and tram stop very close if you want to reach for instance the railway station or Bahnhofstrasse with its department stores and jewellery shops.
If you intend to stay in downtown Zurich it will be hard to find a hotel which is more quiet than Hotel Roessli or Florhof. To be honest I don't know any hotel which isn't influenced either by nearby restaurant terraces, bars, traffic or trams. Zurich is a lively city and people like to go out. If a very quiet location is important to you I advise to look for a hotel outside the city center such as Hotel Zuerichberg.