Camera zoom in and zoom out of the target with smoothfollow

Hi everyone ... i want to make camera zoomin and zoomout of target with smoothfollow script, i have distance and height from camera i try it, but i have problems

 void On_PinchIn(Gesture gesture){
           distance += gesture.deltaPinch*10;
              distance = Mathf.Clamp(distance, 5, 20);
 
           y = ClampAngle(y, 20, 80);
           
           Quaternion rotation = Quaternion.Euler(y, x, 0);
           Transform position =  rotation * Vector3(0.0, 0.0, -distance) + target.position;
     
           transform.position = Vector3.Lerp(transform.position, position, 5*Time.deltaTime);
           transform.rotation = rotation;
     }

any idea for that..