Zion is special, no doubt about it, but I don't think I'd be comfortable with him as our star going forward, not enough to trade Ayton for him. He should be a great pro and has higher upside than Ayton does but I still worry that he's a knee injury or two away from being just pretty good. I don't think he'll bust. At worst, he's probably a likable version of Draymond Green but at best he's got Rodman's defensive skills and Barkley's offense combined with young Shaq's personality and likability. After watching Amare be robbed of his athleticism though I wouldn't wager our future to get a front seat to see it happen again.
So no, I wouldn't trade Ayton for Zion. I think another team might consider if the Suns made the offer but I don't know if another team would gamble on that though. Since the Suns are sending Ayton as their lottery representative it would be a really bad look to send him, get #2 to be able to take Ja, and trade Ayton to whoever for the pick to take Zion.