As a natural reflex I double clicked the divider between project window and lower zone and expected the lower zone to disappear. Suprised it did not. Therefore this small FR 
Double click the border of the different zones to hide them.
There’s already extensive keyboard shortcuts, please don’t add this…
I’m always a little puzzled by people showing up in someone else’s feature request and saying “please don’t do this”
If they added the option to hide by double clicking the border, and you wouldn’t use it, how exactly would it affect you? And don’t say you’d do it by accident. The border is like a few pixels thick. Plus… keyboard shortcuts to reopen it.
That said, I’m basically indifferent to this request, as I do assign my own shortcuts to everything, but I see how it makes sense.
Just FYI: “CTRL-ALT L” does the left one, “CTRL-ALT R” the right one, and “CTRL-ALT E” the bottom one.
Once you’re there, “CTRL-ALT left arrow”, " “CTRL-ALT right arrow” lets you navigate within the in-focus zone.