Quote from : Captain America: The Winter Soldier Movie

Natasha Romanoff: After WWII, S.H.I.E.L.D. recruited German scientists with strategic value.
Dr. Arnim Zola: So I could help their cause. I also helped my own.
Steve Rogers: HYDRA died with the Red Skull.
Dr. Arnim Zola: Cut off one head, two more shall take its place.