iPhone 12 is stuck, with screen zoomed in

Double tap the display using three fingers.

Hey there,

Try pressing twice on the screen with three fingers if it doesn’t work , force restart by this steps:

Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the side button. When the Apple logo appears, release the button.

See if this link helps...

If your iPhone won't turn on or is frozen - Apple Support