How can I rotate the camera angle in two windows at once?

You can do this in one of two ways:

1 - In Navigator>Animations>General, select Play Animations in all 3D Views

2 - If you want to move the camera in more than one but not all of the 3D windows, right click in one of the 3D windows and choose Camera>Link with> then choose the name of the 3D window you want to play the animation in. Repeat for other windows as needed

Option 1 will only show the same rotations/zooms when an animation is playing. When cameras are linked using Option 2, the linked windows will use the same camera angle and update automatically whenever you pan/rotate/zoom in any of the linked views, whether manually or when playing an animation