This is designed to draw attention to the person currently talking and is mostly effective.
Zoom does allow you to change this behaviour if you want to though.
To get into the parameters, select your user icon in the top-right corner, then select parameters.
To access Zooms prefs, choose your user icon, then on prefs in the dropdown menu.
Tip: This setting is only effective when youre using the Active Speaker view.
It will not have any effect if you use the Gallery view.
Tick the labelled See myself as the active speaker while speaking checkbox in the Video controls.