At the beginning of the season, if you had been offered to trade Joshua Roy and a surplus for Trevor Zegras, you probably would have said yes without hesitation.
Now that we've seen what Josh is capable of, we become more reluctant to trade him, especially since the Ducks' forward is having a forgettable season.
Indeed, after two seasons with over 70 points, Zegras has been injured and hasn't really impressed for the rest of the time. He only has 7 points in 20 games, which is 2 less than Roy in the same number of matches.
Now that we know Joshua has a great offensive flair and seems capable of translating it to the NHL level, I would be surprised if the Canadiens decided to trade him, especially for a struggling player.