Can Apple change or add new gesture for enabling zoom in iOS?

Hi,

I am a visually impaired person and zoom feature in iOS is a must for me.

I have been using iPhone for many years since 3GS. Now I am using 6Plus with iOS 9.

Personally I highly appreciate with the iOS zoom feature, but the 3 fingers double taps gesture make me mad all the time.

I think people who really use zoom everyday would understand that detection of 3 fingers double taps is not detected correctly all the time, sometimes not functioning properly, sometimes with slow detection and response, and when working with the keyboard is even harder. Also you must have both hands Free to use this feature, that mean I can't read message under rain when waiting someone in street as I need to hold my umbrella, and that is not the only situation that I am facing, it's just an example.

I wonder if Apple can change this gesture or allowing us to make a customised one. Says, drawing a circle with my thumb or maybe triple tap with thumb. Maybe you can think of a better one.

Thanks