You're very good at predicting the past, but Parise came out of college and had a totally unremarkable AHL debut - he led the team in points but he didn't score goals - and then he had an unremarkable rookie season at age 21. There's absolutely no way knowing what I know now that I would've predicted he'd score 30+ goals in his next season.
The only thing that stats in a previous league tell us is what we think a player might do in the next season at a higher level. Once they're playing in that higher league, we can start to consider what those numbers mean - most importantly, the most relevant data point is the most recent season. I don't care very much what Zacha's stats were in the CHL at this juncture - they're much less relevant than his NHL performance.
Guys who are 20 and putting up the numbers Zacha is tend to improve into something better. They don't tend to become 1st line players, though.
The only point of bringing up Parise and Elias etc. to Zacha is merely to note that Devils forwards have typically been older than Zacha when they've become NHL regulars. Searching hockey-reference for 20 year old forwards playing for the Devils gets me Gomez, who won the Calder as an h-r 20 year old (turned 20 before 2/1 is a 20 year old according to h-r), Zacha, Tedenby, and Josefson are the only Devils who've played more than 41 NHL games as an h-r 20 year old since Shanahan in 89. Obviously Bratt and Hischier will next year, but this is not something we've seen a lot of.