Often when showing my screen to someone else or connecting to a project, I
have to adjust the zoom level of my current window by hitting Cmd + a
bunch of times. Once I am done I usually do some guess work to get the
screen size back to what I am used to, hitting Cmd - a couple times.
There is an easier way.
Hitting Cmd 0 will return the window back to its default zoom level.
h/t Jake Worth