The 21-year-old left Selhurst Park at the end of last season to join the Red Devils in a £15m deal.
After failing to make a Premier League start before the New Year, United loaned out the England international winger to Cardiff City, where he has yet to score in nine appearances in all competitions.
Reports have claimed that United may be ready to cut their losses on Zaha when the transfer window reopens, and Parish has confessed that Palace would welcome him back if they avoid relegation.
"Wilf's a fantastic player, I certainly think we would be interested," he told Sky Sports News. "United have not said anything official, he's their player, but if a player like that did become available then I am sure we would be interested.
"If we are fortunate enough to stay in the division, we will be looking to kick on and establish ourselves and try to get up to mid-table and be a bit more comfortable.
"Wilfried is a player who is worthy of the division and is a player who could help anybody. We saw him come on for Cardiff at the weekend and he changed the game, so if a situation arose for that kind of player, of course we would be interested."
Zaha scored eight goals in 46 games last season to help Palace gain promotion from the Championship.