Gessnerallee is very central so that's good. To one side there's Bahnhofstrasse and the old town and to the other side, if you cross the river, the area is a bit more trendy/hipster-y or whatever you want to call it.
Having grown up here I never know what to recommend to tourists as I have a hard time getting into that tourist mindset.
For a nice walk you can follow the river from Gessnerallee to Brunau and out of the city into the woods. If you want to do a short day-trip you can also go up to Uetliberg for the view. Personally I haven't been all the way up in close to 20 years but I hear my friends who come to visit like it.
I don't know what kind of photography you're into but if you like to do street photography stuff I recommend going to Hauptbahnhof late in the afternoon/early evening on a sunny day. Lots of people running around and the light coming in from the windows of the hall is beautiful.
By the way, that store Eschenmoser is in only a 10 minute walk away from Gessnerallee.
