FLICKERING SCREEN

The dark band on top on the zoom call may due to the camera orientation or type of camera used on the video itself or the camera video setting itself. Most Macs are set for 16:9 ratio screen resolution where non-HD video is usually at a 4:3 resolution. Cell phone videos are typically oriented portrait instead of landscape which creates the black screen borders.

Ghosting on the image on a zoom call sometimes is due to the lag of the internet connection in the zoom call being significant. Or other internet functions taking a lot of bandwidth. iCloud with larger than standard 5 GB cloud accounts when backing up large folders can create significant background lag to the point of freezing.

So can software downloads. The other big problem is optimization tools. Advanced Mac Cleaner and MacKeeper are the worst "optimization" tools as they actually delete the important files that keep the speed of the machine optimized.

If neither of these potential causes for problems exist, run the hardware diagnostics to make sure there isn't anything detectable there:

Use Apple Diagnostics to test your Mac - Apple Support

If there are no obvious hardware issues, run Etrecheck, and report the results back here. Etrecheck and how to report is documented here:

Etrecheck - the handy reporting tool for … - Apple Community

Please do not use all uppercase. Most people on the internet will view that as shouting, plus it is hard to read.

Let's start by finding out, are you talking about the built-in display of a laptop or an external display?

If external display what connectors are you using to connect the display?

Is the computer under warranty?