Upvote:2
There have been a bunch of fictional movies involving zeppelins and other airships.
I once stumbled upon a scene of a zeppelin attack on London on television. It turned out to be from the famous Howard Hughes movie Hell's Angels (1930). And I don't think it was the only fictional movie to depict a zeppelin attack.
So it is possible that a documentary would use images of a zeppelin attack from an old war movie. And it is possible that newsreels during World War I used special effects to depict zeppelin attacks on London, and the documentary used some of that more or less fake newsreel footage.