Gomamon

Q:You activate an effect that reads "Return 1 of your opponent's Digimon to their hand. Trash all of the digivolution cards of that Digimon" to return an opponent's Digimon to their hand. When your opponent's digivolution cards are trashed as a result, can you activate this card's effect?

A:No, you can't. "Trash all of the digivolution cards of those Digimon" is an explanation of what happens to the digivolution cards of the Digimon when it returns to their hand. It doesn't count as trashing digivolution for the purposes of this card's effect.