Question

Does the transfer of Event: Celebi, Entei, Suicune, Raikou, have to be via Relocater to trigger Zorua/Zoraork?

Answer 1

Nope the Poketransfer can work to. Source: Personal experience.

Answer 2

Yes.

These Pokémon can only trigger their respective in-game events if transferred to Generation V via Relocator; they cannot activate these events if transferred via Poké Transfer.

Relocator (Bulbapedia)