Would Ditto transform into Pikachu or Zoroark?

Question

For example, if a Zoroark was illusioned into Pikachu, and an Impostor Ditto came out, what would happen;
1: Ditto would transform into Zoroark
2: Ditto would transform into Pikachu
3: Ditto would transform into Zoroark disguised as Pikachu

Answer 1

The move transform would just fail if used on a illusion. For imposter, it will just stay as a ditto when sent out.

Thanks, Halcyonic Falcon!