translate a point between two cameras

I have a script which limits camera movement to within a defined range. Unfortunately, it only works on the first camera, and there are up to four orthographic cameras in my game.

I have been unable to adapt the script to work with multiple cameras, so I figured that the next best this would be to translate the points from the four corners from the first camera's viewport to world position, then from the world position back to the viewport of cameras 2, 3 and 4. However this doesn't appear to be working.

 SpriteRenderer spriteBounds = GameObject.Find("Map").GetComponentInChildren<SpriteRenderer>();
         float leftBound =0;
         float rightBound =0;
         float bottomBound =0;
         float topBound = 0;
 
         if((trackPlayer1 == null))
         {
             camPlayer1.transform.position = this.transform.position;
         }
         else
         {
             float vertExtent = camPlayer1.orthographicSize;
             float horzExtent = vertExtent * (Screen.width * (camPlayer1.rect.width * 2)) / Screen.height; //I guess the problem is here... but how do I fix this??
 
             leftBound = (float)(horzExtent - spriteBounds.sprite.bounds.size.x / 2.0f);
             rightBound = (float)(spriteBounds.sprite.bounds.size.x / 2.0f - horzExtent);
             bottomBound = (float)(vertExtent - spriteBounds.sprite.bounds.size.y / 2.0f);
             topBound = (float)(spriteBounds.sprite.bounds.size.y / 2.0f - vertExtent);
 
             camPlayer1.transform.position = new Vector3(Mathf.Clamp(trackPlayer1.transform.position.x, leftBound, rightBound), Mathf.Clamp(trackPlayer1.transform.position.y, bottomBound, topBound), camPlayer1.transform.position.z);
         }
         if((trackPlayer2 == null))
         {
             camPlayer2.transform.position = this.transform.position;
         }
         else
         {
    
             leftBound = camPlayer1.ViewportToWorldPoint(new Vector3(leftBound, 0, 0)).x;
             rightBound = camPlayer1.ViewportToWorldPoint(new Vector3(rightBound, 0, 0)).x;
             bottomBound = camPlayer1.ViewportToWorldPoint(new Vector3(0, bottomBound, 0)).y;
             topBound = camPlayer1.ViewportToWorldPoint(new Vector3(0, topBound, 0)).y;
 
             leftBound = camPlayer2.WorldToViewportPoint(new Vector3(leftBound, 0, 0)).x;
             rightBound = camPlayer2.WorldToViewportPoint(new Vector3(rightBound, 0, 0)).x;
             bottomBound = camPlayer2.WorldToViewportPoint(new Vector3(0, bottomBound, 0)).y;
             topBound = camPlayer2.WorldToViewportPoint(new Vector3(0, topBound, 0)).y;
             
             camPlayer2.transform.position = new Vector3(Mathf.Clamp(trackPlayer2.transform.position.x, leftBound, rightBound), Mathf.Clamp(trackPlayer2.transform.position.y, topBound, bottomBound), camPlayer2.transform.position.z);
         }