Zoom in to provide more detail

I am trying to use this library to implement zoom in and zoom out to say an arm. The idea is that as I zoom in, the app will show a more detailed picture of the inside of the arm. I a trying to place another image on top of the imageview when the zoom in event happens.
I was wondering if someone could point me out to which function is the one that returns that zoomed in imageview so that I can modify it for my need.
Thank you