Necrotic Hex

• WWizards of the Coast2020-11-10
  Official Ruling
  Let's say everyone controls lots of creatures. As Necrotc Hex resolves, first the player whose turn it is (likely you) chooses which six creatures they'll sacrifice, then each other player in turn order does the same, knowing the choices of players before them. Then all creatures are sacrificed simultaneously. Finally, you'll create the six tapped Zombies.
• WWizards of the Coast2020-11-10
  Official Ruling
  You'll create six tapped Zombies no matter how many creatures you sacrifice.

Rulings via Scryfall