The commands you entered should work. I wonder if perhaps AutoBrightness is not the thing you are looking for.
Zorin OS comes with another feature that changes the tone of the desktop vs. night / day.
Can you please clarify what it is that you are seeing and wish to change?
You may check in Zorin Appearance for something like "Night mode".
Or Zorin-Appearance > theme > Background - the middle button that has a Sun / Moon icon.