Zoom option doesn't work for TV Shows. It only works for Movies. My device has 18:9 aspect ratio. While watching Netflix or Hotstar, I can just Zoom any 16:9 video to fit into 18:9. But in Prime Video it doesn't work. Even the shows that are literally shot in 18:9 (The Boys, Made In Heaven, etc) doesn't play in 18:9... instead they play with black bars on Left & Right as well as Top & Bottom. Which looks awful (check screenshots). It degrades the whole watching experience.
16:9 Shows-
18:9 Shows-