I know the card is visually difficult, being a flip card, but a creature that says 4B: Zombify a creature is worth the effort and the reading
Oh, and if you need someone dead quick, theres always Tyrannex Rex, right
But there are over 500 unique beasts in Magic, so its somewhat daunting to choose the best of the best
Assuming you only cast two Hydras per turn from that point on, youre still gaining eight mana every single turn just by having them out
Now in Commander Land, due to the color-identity rule, you can't run these tricks outside of a Commander deck that runs all three colors (so it would have to be either a five-colored deck or Temur)
Green doesnt offer the best brawlers until at least Turn 3, so I recommend evaluating it as a mid- to late-game kill spell instead of comparing it to something like Smite the Deathless