Why is the simple zoom via increasing FoV not working?

EDIT: Far better formatted version on StackOverflow = https://stackoverflow.com/questions/71889482/zoom-cameras-aim-is-off-quaternions-completely-baffling-me

Hi everyone!

I am using the following script, which I got from Unity's forums:

 using UnityEngine;
 
 [AddComponentMenu("Camera/Mouse Look")]
 public class MouseLook : MonoBehaviour
 {
     Vector2 _mouseAbsolute;
     Vector2 _smoothMouse;
 
     public Vector2 clampInDegrees = new Vector2(360, 180);
     public bool lockCursor;
     public Vector2 sensitivity = new Vector2(2, 2);
     public Vector2 smoothing = new Vector2(3, 3);
     public Vector2 targetDirection;
     public Vector2 targetCharacterDirection;
 
     // Assign this if there's a parent object controlling motion, such as a Character Controller.
     // Yaw rotation will affect this object instead of the camera if set.
     public GameObject characterBody;
 
     private MainCamera        mainCamera;
 
     void Start()
     {
         // Set target direction to the camera's initial orientation.
         if (targetDirection == null)
         {
             targetDirection = transform.localRotation.eulerAngles;
         }
 
         // Set target direction for the character body to its inital state.
         if (characterBody)
             targetCharacterDirection = characterBody.transform.localRotation.eulerAngles;
 
         mainCamera = gameObject.GetComponent<MainCamera>();
     }
 
     void Update()
     {
         // Ensure the cursor is always locked when set
         if (lockCursor)
         {
             Cursor.lockState = CursorLockMode.Locked;
         }
 
         // Allow the script to clamp based on a desired target value.
         var targetOrientation = Quaternion.Euler(targetDirection);
         var targetCharacterOrientation = Quaternion.Euler(targetCharacterDirection);
 
         // Get raw mouse input for a cleaner reading on more sensitive mice.
         var mouseDelta = new Vector2(Input.GetAxisRaw("Mouse X"), Input.GetAxisRaw("Mouse Y"));
 
         // Scale input against the sensitivity setting and multiply that against the smoothing value.
         mouseDelta = Vector2.Scale(mouseDelta, new Vector2(sensitivity.x * smoothing.x, sensitivity.y * smoothing.y));
 
         // Interpolate mouse movement over time to apply smoothing delta.
         _smoothMouse.x = Mathf.Lerp(_smoothMouse.x, mouseDelta.x, 1f / smoothing.x);
         _smoothMouse.y = Mathf.Lerp(_smoothMouse.y, mouseDelta.y, 1f / smoothing.y);
 
         // Find the absolute mouse movement value from point zero.
         _mouseAbsolute += _smoothMouse;
 
         // Clamp and apply the local x value first, so as not to be affected by world transforms.
         if (clampInDegrees.x < 360)
             _mouseAbsolute.x = Mathf.Clamp(_mouseAbsolute.x, -clampInDegrees.x * 0.5f, clampInDegrees.x * 0.5f);
 
         // Then clamp and apply the global y value.
         if (clampInDegrees.y < 360)
             _mouseAbsolute.y = Mathf.Clamp(_mouseAbsolute.y, -clampInDegrees.y * 0.5f, clampInDegrees.y * 0.5f);

             // ********************* PROBLEM LINE ********************
         transform.localRotation = Quaternion.AngleAxis(-_mouseAbsolute.y, targetOrientation * Vector3.right) * targetOrientation;
 
         // If there's a character body that acts as a parent to the camera
         if (characterBody)
         {
             var yRotation = Quaternion.AngleAxis(_mouseAbsolute.x, Vector3.up);
             characterBody.transform.localRotation = yRotation * targetCharacterOrientation;
         }
         else
         {
             var yRotation = Quaternion.AngleAxis(_mouseAbsolute.x, transform.InverseTransformDirection(Vector3.up));
 
             transform.localRotation *= yRotation;
         }
     }
     }

I am trying to do a simple zoom via increasing the FoV. Unfortunately, however, the MouseLook script is messing with the zoom. I managed to track down the problem to the line I marked with "PROBLEM LINE" in the script above, namely transform.localRotation = Quaternion.AngleAxis(-_mouseAbsolute.y, targetOrientation Vector3.right) targetOrientation;

Unfortunately I can't fully understand what the script is doing. How can I get them to work together? The zoom (I simply increase FoV then have the transform look at the point where the mouse is) works fine without the script.

Thanks a lot!