HI, my iphone 5 got stuck with zoom on screen. It does not respond to the three finger tapping. It does not reset after power off.

Triple tap the Home button and then uncheck the Zoom option. Alternatively, you may hit Settings - General - Accessibility - Zoom.

If this doesn't help, try resetting your phone.

Try to reset your device. This won't delete your data stored on the phone.

• Press and hold the Sleep/Wake button
• Press and hold on the Home button
• Keep holding both buttons until the display turns off and back on with Apple logo on it.

Alternatively, you may go to Settings - General - Reset - Reset All Settings

https://support.apple.com/en-us/HT201559

Hope this helps!