Default bindings for font size control.

So I just got an 11inch laptop and installed zed on it, and it turned out that the font size I prefer on an 11inch screen is different than what I prefer on a 27inch screen ;-)

It seemed like it would be nice to be able to change that rapidly, so I bound up some keys... but they don't seem to work! Can you investigate why these bindings don't work?

Thanks.