ROTY is still a a bigger achievement for me, so he should go for that, however Rikafip has a point, Zion was not able to play many games due to injury and with that, he might loss his chance to compete in the ROTY competition, now he should focus on his team so they'll be in the playoffs.
All Zion can do for now is play as best as he can, and lead his team to playoff, ROTY decision is out of his hands. As i said before, if we base his chances according to previous years, they are not very good, but surprises are always possible.
In 2016/2017 Embiid played 31 game, averaging 20.2 points and 7.8 rebounds. On the other hand, winner was Brogdon, who had 10.2 points and 4.2 assists. ROTY winner with least games so far was Patrick Ewing, back in 1986, with 50 games played in regular season. Carter and Irving won with 50/51, but that was lockout season. So obviously, this is an important part when deciding the winner.
This year, Zion can play at maximum 37 games of the regular season. While his stats are great, main contender so far, Ja Morant, is pretty good too, averaging 17.5 points and 6.9 assists for Grizzlies. Another interesting thing about those two players is that their teams will fight against each other for that 8th spot, and maybe that could be a factor in the end. Whoever gets his team in the playoff (and keep playing at current of better level), gets ROTY. I think that would be fair.