In iPhone, the 6 & 7 series have the display zoom option. If we enable it then the screen size will be changed accordingly in points.
In case of iPhone 6, 6s, 7 the screen size will change from 375 × 667 points to 320 × 568 points which is iPhone 5, 5s's actual screen size in points.
In case of iPhone 6+, 6s+, 7+ the screen size will change from 414 × 736 points to 375 × 667 points which is iPhone 6, 6s, 7's actual screen size in points.
Now I'm little bit confused here. As we all know the Points is based on coordinates of device's physical screen. Then how the actual screen size of iPhone is changing in display zoom option without changing the screen's width and height physically? I mean whats the logic behind this.
Look I may be wrong with the concept of screen size in Points I'm explaining here. In that case, please explain the original concept.
The points are the logical resolution that the OS presents to the applications. It is then mapped onto physical pixels, usually in a 2x resolution, but for example the Plus models do not have enough pixels for a straight translation, so there is some mismatch there already. That mapping is done by the OS automatically.
The zoom options set a lower logical resolution (forcing for example apps to render for a virtual 4-inch screen even though the device has a bigger physical one), making everything appear larger.
Either way, apps do not get to render pixels directly. They output according to virtual points.