Iam using zorin on an 8gb ram laptop which shouldn't lag that much and most of the time feel a bit of lag
After some digging and i find a process called "Isolated Web Co" taking nearly a 1gb and half of memory and i don't know from which app does this come from but it starts always with firefox
My first question is, what extensions do you have installed? I use Firefox constantly and never see that process. Are you using the incognito mode?
You might try, and I know you don't WANT to be in the terminal but bear with me, sudo apt remove firefox -y && sudo apt install firefox -y. This will work as long as Firefox isn't a snap or flatpak package (Zorin defaults to apt installed applications for most of them). Try it before signing in and see if there are any "leaks". If not, it's an extension that you have installed (which I really do think is the issue). Which one I could not tell you.
It seems this is a fairly common thing, depending on visited sites and possibly an issue with firefox. It appears that it is mostly mac users complaining of it, though linux mint and windows were mentioned as well. The mozilla devs are the ones that will have to resolve this, Not Zorin. It is an application issue, not an OS issue. You can read up on some things that will help you diagnose the issue here.
The only thing I can tell you is to uninstall firefox and reinstall. Maybe try chrome browser as well, to see if you get the same results. I listed the commands to un-re-install above.
Yeah i did re-install firefox from the terminal and it appeared to be that the problem is in firefox itself as you said, because i removed all add-ons (extensions) but it didn't help solving the problem either
I didnt experience the same thing on windows so i guessed its a linux issue and the forums i viewed on ask-ubuntu were useless for me so i posted the issue here
So my only option is to move into another browser but not chrome, I already ditched chrome because of its anti ad-block manifest-3
As I have said, I use Firefox, religously and have not run into this issue. I'm wondering what is it about certain hardware that causes this or certain sites visited (though you show Google search results, so I'm thinking it's a driver that is causing the leak) . Not knowing how Firefox is assembled leave me at a disadvantage to the possible reasons for this memory leak and the content process never terminating.