>> To enable Zoom, use three fingers and double-tap the screen.
>> To increase the level of Zoom, use three fingers to double-tap and hold, then move your fingers up or down on the screen to increase or decrease magnification.
> If I enable zooming for users, every tap on every mobile device is going to get slower for every user. Is that in the interest of better UI?
Yes they do!
https://support.apple.com/en-gb/HT204390
>> Zoom
>> To enable Zoom, use three fingers and double-tap the screen.
>> To increase the level of Zoom, use three fingers to double-tap and hold, then move your fingers up or down on the screen to increase or decrease magnification.
> If I enable zooming for users, every tap on every mobile device is going to get slower for every user. Is that in the interest of better UI?
I do not understand your point.