Ok, then what we may need to look at is the scaling perameters of the Zorin Icon theme.
As you are using Zorin Lite, you can enter into terminal
This will prompt for password, then open an elevated privilege Thunar. The third button over from the far left side of the toolbutton is an Up Arrow. Whack that once or twice.
You should now be seeing the topmost level of Root, including the directory /usr
Open that, then /share, then /icons
From here, I would do a split screen if one monitor, or one open window on each monitor, but- You want to navigate to Zorin icons and to Gnome icons. In each directory, you will find index.theme
Open those for each and compare the Directory list and the scaling list.
Scroll down to where you see Directory List. Look for typoes or Missing Entries in the directory list, comparing against the Gnome (Known working) index.theme Directory List.
If all is well, scroll down to where you see
Check that size and minsize are as shown above, for each of the Scalable Sections.