So i put my Z fold 4 in an enclosed soft case inside my bag (closed position). The next day when i took it out and opened the main screen, i found a long straight scratch from the top to the bottom of the main screen. Anyone knows what happened? Should i just replace the factory screen protector with a new one?
Looks like your screen is broken when zooming in on the photo. Samsung won't fix it under warranty so you don't have much to lose by removing the screen protector. I think doing so may cause further damage though.
My advice comes from being a UK Samsung phone user.