Mikel stopped by to explain what happened with cover:
As I’ve already explained (a week ago in my blog), it was not an editorial choice to make her show her cleavage, but to match the interiors. The solicit cover was made BEFORE the series, and this corset appeared solely in issue #1. Then, Zee’s look has been slightly different in each issue, with black corsets, white corsets, black jackets and so. I’m sorry if someone is offended but there’s not any intention other than match the interior pages.
And indeed Zatanna is wearing that outfit, among others, in book: