Hearthpwn

Zephrys is objectively the best card in the game, and by quite some margin too. I would run Zephrys over Kazakus any and every day of the week. Kazakus requires you guess what you're going to need whereas Zephrys give you what you actually need based on actual board state.

One way or another Zephrys wins games time and time again. Need Bloodlust or double attack for lethal? Need a board silence? Flamestrike? Zephrys has literally never failed me. I can only guess you're playing it on curve or when you don't actually need to. Be patient and wait for the right time to play it.