Symptom:
Google Earth flickers/screen is jittery when zooming in/out or just moving around.
Solution:
From within the Google Earth app - go to Tools >> Options. Change Graphics Mode from OpenGL to DirectX, change Anisotropic Filtering to High.
Inside Nvidia Control Panel >> Manage 3D Settings >> Global Settings:
Preferred graphics processor - Use high-performance NVIDIA processor
Max Frame Rate - cap at 30 or 60 fps
Power management mode - Prefer maximum performance
Texture filtering - Quality - High performance
Other options can be fine-tuned as required, although the above should be more than enough to ensure smooth performance.