Very strange. I checked with some friends that own a ZTE and they can't find any special setting that could cause those squares. I wonder if the culprit could be an app that came preinstalled. Do you recall updating any app right before they started? Do you have any cleaner, booster or similar app in your phone? Can you see any service activated in the accessibility settings?I factory reset my phone and the problem still consists I don't know if that would help find the answer to my problem