First full day using Zorin OS so I am attempting to transfer as much from my old system to my new system. (Logins, browser tabs, etc.)
While performing this task, I've come to the observation that uploading via a Chrome browser (I'm using Brave browser, which is chromium based) to Google Drive doesn't work. I get a "file unreable" error within Drive.
However, it does work in Firefox.
Has anyone experienced anything like this?
Have come across similar complaints, including one quite recently here on this forum where the file was present, but gibberish.
You would think that Chromium and Google would get along just fine. It really makes you wonder.
Ordinarily (on Windows) it worked just fine. There was no dramas whatsoever. I just can't quite figure it out...
I am not sure, either. I no longer use Chrome, Chromium or Vivaldi due to the strange bugs. I ditched Firefox a few times; but it is what I use now simply because it generally Just Works.
You might check on the Chrome or Chromium support boards where there are folks much more experienced in the ins and outs of the Browser. That Firefox does work properly shows that this is not Zorin OS side.
This is not a "not our problem" response as much as it is an "I am utterly unqualified to try to help" problem.
It may be that other users here are better qualified, but I would check the Chrome forums anyway just for a faster chance at a solution or suggestion.
Shall do. The problem is now a little more defined in that images will upload, but videos won't. Or at least the MP4 I was trying to upload won't. 
I'll keep searching.
I stop using Google drive and Chrome/Chromium for some years now.
But if you do no mind to change your cloud storage, MEGA works quite well. It has a generous storage and Linux is well supported. It even gives you a Nautilus integration which I have been using without any issue on Zorin as well as Mint Linux.
I just created one for free there. Much better than Google Drive.
Would love to. Unfortunately I need to use it for work. Company policy. 
I can understand.
For the same reason, I cannot be 100% Windows free. My solution is virtualising Windows for last 6 years.
I'm responding a bit late but I hope it's better late than never. Is your chromium based browser a Flatpak/Snap application or did you install the .deb file?
Sorry for responding late, myself. 
I'm a total newbie. How would I check on that? How do I know the difference?
Method one:
Open Software Store and click on the "Installed" option at the top.
Scroll down to Chromium Browser and click it open.
Scroll down to Details at the bottom and look at Source
If Source says "ubuntu-bionic-universe" or "ubuntu-focal-universe" then it is installed by Repo.
If Source says Snap, then it is a snap.
If Source says Flatpak - then Flatpak.
Method Two:
In terminal enter
snap list
To list all installed Snaps
flatpak list
To list all installed Flabpaks
Check if Chromium is on either list.
In software Center you (in most cases) decide if it's "Repo" or Flat/snap. If you have the option to choose it will show itself in upper right corner.
This was introduced in Zorin OS 16.
Aah, I forget that not all have Z16 installed.
Not for the Cloud upload, but when I installed Only Office in Flatpak, I could not access to files locate in a separate disk as well as network drives.
I think it is possible that your Chrome has been installed by either Flatpak or SNAP then you cannot access to certain drives due to the built-in sandboxing nature of those installers.
