Graphic drivers are not working as it should

When I minimize a page, it is not smoothly minimizing pages. Graphics not working smoothly. Using Intel HD Graphics 620 on i5-7200u. This happens in Ubuntu also.

onboard intel graphic cards aren't the strongest to do 3D.

What Zorin OS are you using? IF Core or Ultimate you can disable animations. I'm not sure about lite...

Go to Zorin Apperance --> Interface and disable animations

I don't think that this is about how strong my graphic card is.

What version of Zorin are you using? If Z16 beta you could try update the driver.