This is the deck I'll be using in the Tavern Brawl this week, it will abuse the double deathrattle to become a better ZooLock deck.
Use Sylvanas Windrunner if you start losing the board or you have nothing else to play.
Try to use Life Tap as many times as you can.
Play Loot Hoarder as soon as you can, so you won't run out of steam.
The idea for Undertaker is that you play it and next turn you play 2~3 cards with deathrattle, so you can trade the undertaker with bigger minions, getting the most value out of a 1-drop.
Use Silence to crush your opponent's dreams.
Check out bellow Caffry's video showing this deck in action! Also, check some other videos on his Youtube channel too!
Have fun! Happy Tavern Brawl!