How to pan/scale the contents within a GUI area?

I want to have a zoom effect within a specific area in a EditorWindow, something like a zoomable scrollview.

The folowing snippet does the job for scaling the contents but I can't find a way to handle independently the new clipping rect and the contents origin.

 public class EditorZoomArea
 {
     private static float kEditorWindowTabHeight    = 20;
     private static Matrix4x4 _prevGuiMatrix;

     //Starts the zoomable area
     public static Rect Begin(float zoomScale, Rect zoomRect, Vector2 zoomOrigin)
     {
         GUI.EndGroup(); //End the group that Unity began so we're not bound by the EditorWindow

         zoomRect.y += kEditorWindowTabHeight; //Account for the window tab
         zoomRect.height -= kEditorWindowTabHeight + 3; //Account for the window tab

         Rect clippedArea = zoomRect.ScaleSizeBy(1.0f / zoomScale, zoomRect.center);

         //GUI.BeginGroup(clippedArea);
         GUI.BeginGroup(new Rect(0.0f, kEditorWindowTabHeight, Screen.width, Screen.height - (kEditorWindowTabHeight + 3)));

         _prevGuiMatrix = GUI.matrix;

         //Perform scaling
         Matrix4x4 translation = Matrix4x4.TRS(-zoomOrigin, Quaternion.identity, Vector3.one);
         Matrix4x4 scale = Matrix4x4.Scale(new Vector3(zoomScale, zoomScale, 1.0f));
         GUI.matrix = scale * translation;

         return clippedArea;
     }


     //Ends the zoomable area
     public static void End()
     {
         GUI.matrix = _prevGuiMatrix;
         GUI.EndGroup();
         GUI.BeginGroup(new Rect(0.0f, kEditorWindowTabHeight, Screen.width, Screen.height - (kEditorWindowTabHeight + 3)));
     }
 }

Is there a way to do this, maybe using a scroll view or two nested clipping rects?