Warner Bros. Discovery’s announced separation follows the industry’s latest M&A trend. In this case, separation is easy. Successfully shaping what comes next is the hard part.

Four years ago, David Zaslav clinched a debt-heavy deal to merge cable mainstay Discovery Inc. — which he’d run since 2006 — with what was then called WarnerMedia. The story he told investors was that the two entities’ diverse array of media assets “are better and more valuable together.” He doesn’t believe that anymore.

The film and television giant will turn its cable networks, including CNN and TNT, into one company and its streaming and studios business into another.