Zacama, Primal Calamity

• WOTC Official Reminder Textofficial rules
  Vigilance — Attacking doesn't cause this creature to tap.

• WWizards of the Coast2018-01-19
  Official Ruling
  Zacama's triggered ability triggers if you cast it from any zone. It doesn't trigger if you put Zacama onto the battlefield without casting it.
• WWizards of the Coast2023-07-28
  Official Ruling
  Zacama's damage-dealing ability can be activated during combat, perhaps targeting a creature blocking it. If all creatures blocking Zacama are destroyed, its combat damage is assigned to the player, planeswalker, or battle it's attacking because of trample. If the blocking creatures are dealt nonlethal damage, that damage is considered when assigning trample damage.

Rulings via Scryfall