Return target nonland permanent to its owner's hand. Then that player discards a card if you control a Zombie.
4/8/2016 The card returned to its owner’s hand may be the card they discard. If it’s the only card in that player’s hand, it must be discarded.
4/8/2016 Compelling Deterrence targets only the nonland permanent. If that permanent becomes an illegal target, Compelling Deterrence doesn’t resolve and that player doesn’t discard a card.
4/8/2016 If you target the only Zombie you control with Compelling Deterrence, you won’t discard a card.