Zaha joined the Red Devils in January before returning to Palace on loan for the remainder of last season, helping them gain promotion to the top division via the playoffs.
The 20-year-old is yet to feature in the league for David Moyes's side this season, but Holloway pointed to the example of Real Madrid's Cristiano Ronaldo as an example of how good United can be at nurturing talent.
"They produce and nurture talent. I remember Cristiano Ronaldo a few years ago doing 15 million step-overs and getting nowhere, and now look what he does," Holloway told PA.
"Who has helped? I would suggest it is Man United and the attitude of the club. I am delighted for [Zaha].
"He will have to learn about being a big club and what that means but I am so proud of that boy, I can't tell you."
Holloway, who revealed that he tried to sign Zaha on deadline day, will take his Palace side to Old Trafford to face United tomorrow.