Zoolock, as an archetype, will never leave Hearthstone. It is here to stay, but not unchangeable. A few new cards from The Witchwood make up for some exciting new plays.
For example, the synergy between the two new cards -- Duskbat and Bloodwitch -- is obvious. One deals damage to your hero, and the other summons two 1/1 bats. After that, you can start discovering demons by killing one of the bats using Dark Possession.
The rest of the deck consists of well-known demons and buff spells. The deck is as strong as ever and will provide you with many fun hours of gameplay.