I try to get used to Zorin 17 but don't found a way to select a automatic nightmode, so more than light to dark theme. Im Looking for a dark theme + blue light filter, that activate with sunset like in Zorin 16. In Zorin 17 it's only a light to dark mode possible (at least i found no more). And i Know about the quick select option in the icon tray.
Go to settings and then displays. When you click on displays you should get a window with a tab for night light. That is what you want for warmer colors at night.