Okay, I have to give it up for this one. What a great idea.
While I understand that "Man Of Steel" isn't everyone's favorite, I am a huge fan of the film, and one of the things I love about it is the score by Hans Zimmer. There are places in that film where I think Zimmer does some of the best work of his career, big and inspired and beautiful and sweeping and intense and emotional.
It isn't a huge surprise to hear that Zimmer will be working on the score for "Batman v Superman: Dawn Of Justice" as well. I would expect him to continue from the themes that he created for "Man Of Steel," and I assume he and Zack Snyder had a good relationship on that film. It would be enough of an announcement for me to think it was awesome if they just said Zimmer was working on the score. But it's more than that, something entirely appropriate to the nature of the film itself, and it sounds like a perfect idea.