Top 20 NuGet pinch-to-zoom Packages

Xamarin.Android Binding for Natario1's ZoomLayout, 2D zoom and pan behavior for Android View hierarchies, images, video streams, and much more.
Xamarin.Android Binding for Aghajari's ZoomHelper, a library to make any view to be zoomable just like Instagram pinch-to-zoom
A simple pinch-to-zoom ImageView library for Xamarin.Android, based on:
Xamarin.Android Binding for Álvaro Blanco Cabrero's Zoomy, an easy to use pinch-to-zoom Android library