You must first catch a Deino, which can be found on the 1st and 3rd floors of Victory Road by walking, and it has a 20% of showing up. The location of Deino is the same in both Black and White.;
, It would also be wise to have a Pokémon who knows the move False Swipe. No matter how strong your Pokémon is, the move False Swipe will always leave the target with at least 1 hp.
 Dusk Balls are very effective at night, or in dark places such as caves.
 Wild Pokémon may surprise you by having high-damage dealing attacks.
 Beware of moves that burn or poison, as they will drain the Deino's life, possibly before you can capture it.
 Deino doesn't evolve into Zweilous until level 50.

Go to Victory Road.
Carry a Pokémon with you that has status-affecting moves such as Thunder Wave or Hypnosis.
Carry some Ultra Balls or Dusk Balls.
Carry some Potions as well.
Once you come across one, try using False Swipe to lower it's hp down and then putting it to sleep.
Once you have your Deino, start leveling!,
Zweilous doesn't evolve until level 64, at which point, you will have your pseudo-legendary!
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