Camera Control script for Editor

I have begun work on the camera movement for the editor of our game.
So far I have the panning working relatively well, but am having trouble with the camera rotation.

The issue is with the mouse position, I can only get a movement reaction by moving the mouse up or down, and nothing by going form side to side, which leads me to believe that I have left something out, but cannot see anything wrong with it.

What I am trying to achieve is being able to use the middle mouse button to pan around and the right mouse button to rotate the camera on the Y and Z axis.

using UnityEngine;
using System.Collections;

public class CameraControl : MonoBehaviour
{
    public float mouseSensitivity = 0.01f;
    private Vector3 lastPosition;

    void Update()
    {
        if(Input.GetMouseButtonDown(2) || Input.GetMouseButtonDown(1))
        {
            lastPosition = Input.mousePosition;
        }

        if(Input.GetMouseButton(2))
        {
            Vector3 delta = Input.mousePosition - lastPosition;
            transform.Translate(delta.x * mouseSensitivity, delta.y * mouseSensitivity, 0);
            lastPosition = Input.mousePosition;
        }

        if(Input.GetMouseButton(1))
        {
            Vector3 delta = Input.mousePosition - lastPosition;
            transform.Rotate(0, delta.y * 1.0f, delta.z * 1.0f);
            lastPosition = Input.mousePosition;
        }
    }
}

mouse delta only has x and y values
on line 26 you are trying to use delta.z