How to Magnify Your iPhone Screen Temporarily
Step 1. Go to Settings, General, and then Accessibility.
Step 2. Tap Zoom and enable it.
Double-tap three fingers to enable zoom on your screen and you will see the screen immediately zoom inwards. Double-tap again your three fingers to disable it. To navigate around your newly resized window, use your same three fingers to drag around the screen. You should see your iPhone follow your fingers’ motions as you can now see much better.