The one in the gardens of the Fraumünster Abbey. Not much to add after last post, where this landmark was debated almost to death…. Also, not much could be found about it.
150. Fraumünster (2)
Discovering Zurich, one fountain at a time
Zurich 1200 Fountains 
Do you have a picture of the one inside the cloister of Grossmunster? Never managed to see it (only open during weekdays apparently).
I am afraid not… as you said, it is open only on weekdays, which makes the vist a bit more complicated.
Maybe I should take a day off to catch it 😉