How are you applying the "Zoom" to the video?
If you are using the "Pan & Zoom" effect, if you are using Studio 15 Ultimate (possibly also Studio 15 Plus?), as an alternative to "Pan & Zoom", try using the "2D Editor" effect (here, I have Studio 15 Ultimate; in Studio's video toolbox "plugins" tab it's under "Studio Ultimate RTFX").
As to what is causing the video problem with the zoom, one possibility is a recent Intel graphics driver update (I noticed here that Windows Update has installed new Intel graphic drivers on both my desktop and laptop PCs in the last couple of weeks). Have a look in the Windows 10 "Settings" app (Update & Security -> View update history); scroll down to find the list of drover updates and see if there were any updates that coincided with the start of your video problem.
If it does appear that a recent graphic driver update might be the cause of the problem, try rolling back to the previous driver, or look on the Intel website or on your PC manufacturer's website to see if there's a newer one than the one that came from Windows Update.
HTH
Richard