Thank you for contacting Intel Communities.
I am sorry to hear you are having issues with your laptop. You have tried almost all recommendations I could give.
At this point, I would try testing each of the available graphics driver versions available to see if any of them solves the issue:
Downloads for Intel® HD Graphics 620
Check for any BIOS update available.
If the steps above don't fix the issue, I recommend contacting Asus for a possible RMA since this could be related to a defective graphics controller.
Please let me know how it goes.
thank you for your assistance and help.
After several contacts with ASUS service engineers, it seems that the graphics controller was malfunctioning.
ASUS replaced the Zenbook's motherboard to new one, and the issue is gone.