Rotation via script behaves unexpectedly

Hi. I created a house in Blender. In Unity I would like the player to be able to open and close the windows of the house when clicking on a window. I have set the pivot points for the windows to be at the top of the windows (the hinges are at the top and the windows open out and up. I have hidden all the other objects in order not to clutter the pictures.

When I rotate the window object in the Inspector I see that the rotation about the Z axis is what I am looking for. (See Picture 1)

However when I try and write a script to rotate the window the rotation goes funny (See Picture 2).

My script is as follows:

 public class WindowScript : MonoBehaviour {
 
     public bool isOpen = false;
     public float windowOpenAngle = 250.0f;
     public float windowCloseAngle = 180.0f;
     public float movementSpeed = 2.0f;
 
     private Quaternion targetRotation;
 
 
 
     void Update()
     {
 
         if (isOpen)
         {
             //Window is open. Now close it.
             targetRotation = Quaternion.Euler(0f, 0f, windowCloseAngle);
             transform.localRotation = Quaternion.Slerp(transform.localRotation, targetRotation, movementSpeed * Time.deltaTime);
         }
         else
         {
             //Window is closed. Now open it.
             targetRotation = Quaternion.Euler(0f, 0f, windowOpenAngle);
             transform.localRotation = Quaternion.Slerp(transform.localRotation, targetRotation, movementSpeed * Time.deltaTime);
         }
     }
 
 
     public void ChangeState()
     {
         isOpen = !isOpen;
     }
 }
 

What am I doing wrong here? I always get caught out when I deal when rotation. Any help will be appreciated.