The reason that zebras are considered 'unmanagable' is because people compare them to horses, which are similar but definitely not the same. Their habits and personality closer resemble donkeys than horses and thus they require a different method of training. They also have not been domesticated for as long as the horse, and so have more of the wild nature that causes them to show agression if they are threatened and feel as if they can't get away. In truth though they are not untrainable and unmanagable, they just need different training. You can't train a cat like a dog, and you can't train a lion like a tiger, but that doesn't mean they can't be trained.
Back on subject though, those zebras are ADORABLE, OP. Especially the little foal (I'm guessing they're still foals? Or is there another name for them? XD)