Pinch zoom

Hello, I am making pinch zoom with the still ground, which means, that camera size is increasing together with Y position.

Like on these pictures:

There is a code:

 public class PinchZoom : MonoBehaviour
 {
     public float perspectiveZoomSpeed = 0.5f;     
     public float orthoZoomSpeed = 0.5f;     
     public float moveSpeed;
 
     private float fakeMagnitudeDiff;
 
 
     void Update()
     {
         if (Input.touchCount == 2) {
             Touch touchZero = Input.GetTouch (0);
             Touch touchOne = Input.GetTouch (1);
         
             Vector2 touchZeroPrevPos = touchZero.position - touchZero.deltaPosition;
             Vector2 touchOnePrevPos = touchOne.position - touchOne.deltaPosition;
 
             float prevTouchDeltaMag = (touchZeroPrevPos - touchOnePrevPos).magnitude;
             float touchDeltaMag = (touchZero.position - touchOne.position).magnitude;
 
             float deltaMagnitudeDiff = prevTouchDeltaMag - touchDeltaMag;
 
             if (GetComponent<Camera>().orthographic) {
                 GetComponent<Camera>().orthographicSize += deltaMagnitudeDiff * orthoZoomSpeed;
                 GetComponent<Camera> ().orthographicSize = Mathf.Max (GetComponent<Camera> ().orthographicSize, 0.1f);
             }
             if(GetComponent<Camera> ().orthographicSize == 0.1f) {
                 fakeMagnitudeDiff = 0;
             }
             if (GetComponent<Camera> ().orthographicSize > 0.1f) {
                 fakeMagnitudeDiff = deltaMagnitudeDiff;
             } 
             transform.position = new Vector3 (transform.position.x, transform.position.y + (fakeMagnitudeDiff * moveSpeed), -10);
         }
     }
 }

At the first look everything works fine, till player try to do zoom in and zoom out a few times, because it will desynchronize Y position of camera. I think this could be caused by delay of frames, so I want to ask if it is even posible do this feature on this script, or if I must do new pinch zoom script if I want to do this feature. Please help...