I'm talking from personal experience. I used DE when I first started out with chickens. It simply doesnt prevent nor eliminate worms, period. It is ineffective when wet. The innards inside a chicken are wet.
It's a large roundworm. If one has them, most likely your other birds need to be wormed as well. Here's a link on how to worm birds. Please read posts #2 & #4:
https://www.backyardchickens.com/threads/worms-in-chicken-poop.1575508/#post-26765905