Hilaire - who played 293 times for Palace between 1977-84 - says the whizkid can become an Old Trafford regular by helping the Londoners to promotion.
Hilaire, 53, told The Sun: "With a new manager coming in at United, Zaha has the chance against Watford to fire himself into the reckoning at Old Trafford.
"If Zaha puts on a decent performance at Wembley, he could end up starting next season in David Moyes' first team.
"There is no bigger incentive than that and I expect him to be right on the ball."
Hilaire reckons Zaha could go on to become a global superstar at United.
He said: "I compare him to Cristiano Ronaldo - he's got very quick feet and an eye for goal.
"I just hope he gets the chance at United to show what he can do."