Hi @Davide , welcome to the forum!
This topic was quickly discussed here - Enable Gestures in AR - Questions - Babylon.js
The AR camera does not support moving towards or away from the object, as that will contradict the concept of AR - zooming means getting closer, rotating means moving around the object.
What you can do is add a gizmo to the mesh itself so that the mesh itself can rescale and transform. So instead of zooming in, you just make it bigger. You can use any of the gizmos here - Gizmos | Babylon.js Documentation