Launch the Settings app, and select General.
At the bottom of General settings, select Accessibility.
At the bottom of Accessibility, select Triple-click Home.
Select Ask to enable various Accessibility options. (White on Black is handy for night viewing, e.g.)
Exit Settings. Triple-press the Home Button and select Turn Zoom On.
Now, double-tap with 3 fingers to zoom. Swipe up using 3 fingers to zoom in, down to zoom out. A 3-finger drag pans the zoomed-in screen. NoteThis works in any app, even on running movies. Try it!
To disable, triple-press the Home button, and select Turn Zoom Off.