How to implement interface for Opengl application on Android?

Question

Android

Hello!
At school, as part of the course "Computer Graphics", you need to write an application in OpenGL. To my misfortune (or maybe not), I persuaded the teacher to allow me to write for Android using OpenGL ES. Actually, there are no problems with the library itself, the question is in the implementation of the interface. First of all, the following comes to mind: using the built-in Android graphics, drawing UI elements on the screen over a 3D scene and catching touches on them, it seems not difficult, but now catching zoom gestures seems to be not easy. Since I may be wrong, or not know about existing solutions, I ask you this question. Thanks to everyone who remained indifferent!)