Fixing Inverted Camera Controls When Flipped, MouseOrbit

Hello, thank you very much for any help you can provide.

I'm using a script called MouseLook. It's very similar to MouseOrbit, that comes with Standard Assets. I attach MouseLook to my camera and set the Ymin to -360 and the Ymax to 360. My target object is a sphere. This now enables me to rotate infinitely in any direction around the sphere. All good so far.

The problem I'm having is when the camera flips upside down, my 'Left/Right' controls become inverted. So instead of moving mouse left to move camera left, moving mouse left moves the camera right. I want to fix the controls so that they are always consistent visually.

My guess is the logic should be something along the lines of, "If camera is upside down: invert Left/Right controls", and that should cancel out the effect this is having. Unfortunately my scripting/math skills are very beginner.

Here's where I'm at:

 zRotation = GameObject.Find("Main Camera").transform.rotation.eulerAngles.z;
         
         if (axes == RotationAxes.MouseXAndY)
         {
             if (zRotation == 180){
                 
             // Read the mouse input axis
             rotationX += Input.GetAxis("Mouse X") * sensitivityX;
             rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
 
             rotationX = ClampAngle (rotationX, minimumX, maximumX);
             rotationY = ClampAngle (rotationY, minimumY, maximumY);
             
             Quaternion xQuaternion = Quaternion.AngleAxis (rotationX, Vector3.up);
             Quaternion yQuaternion = Quaternion.AngleAxis (rotationY, Vector3.left);
             
             transform.localRotation = originalRotation * xQuaternion * yQuaternion;
             }
             else{
             
             Debug.Log (zRotation);
             
             
             // Read the mouse input axis
             rotationX += Input.GetAxis("Mouse X") * sensitivityX;
             rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
 
             rotationX = ClampAngle (rotationX, minimumX, maximumX);
             rotationY = ClampAngle (rotationY, minimumY, maximumY);
             
             Quaternion xQuaternion = Quaternion.AngleAxis (rotationX, Vector3.up);
             Quaternion yQuaternion = Quaternion.AngleAxis (rotationY, Vector3.left);
             
             transform.localRotation = originalRotation * xQuaternion * yQuaternion;
             
             }

if "zRotation" == 180, than I know my camera is flipped. But I'm having a hard time understanding the code at that point. What's a good way to flip the controls?