This came up in a game recently, where the Nurgle player tried to use this card twice in a region. None of us could really say whether or not that would allow placing a corruption in adjacent regions for each card, or just one because the wording mentions dominating the zone, which you can technically only do once.
So would two cards in the same region cause double the corruption, or would two cards be wasting one as it could only affect a given zone once?