You’re right about having to click not hover.
But I can’t get it to switch to the viewer repeating your process. Only if I click in the viewer or press cmd+3.
Even with the cmd removed from the -/+ keys.
FWIW this seems like a very slow way to zoom into an area. I prefer to first cmd+z (if the area to zoom to isn’t visible), then press z and lasso the area to zoom into. Goes right where I want it very quickly.