I am able to clamp the z rotation of my game object using the code below, but it always changes the y rotation on my first touch. I only want to rotate the z-axis.
private float zRotation;
public void RotateMove()
{
zRotation -= Input.GetTouch(0).deltaPosition.y * rotateSpeed * invert * Time.deltaTime;
// this limits the rotatioon
zRotation = Mathf.Clamp(zRotation, -80, 80);
//this rotates the game obj
lamp2Rotate.transform.eulerAngles = new Vector3(0.0f, 0.0f, zRotation);
}