Is Zenbu legal? Where does the content come from?

Zenbu doesn't upload, store, encode, or host any video files on its own infrastructure — it indexes and links to third-party sources that provide the content. Metadata (titles, synopses, cover art, episode lists) comes from AniList's public API.

If a source is infringing, the most effective takedown is directed at the source itself. See the DMCA page for how to report a link.