Arsenal, Liverpool, Manchester City and Tottenham have all been linked with the 19-year-old in recent weeks.
Palace are determined not to lose Zaha and the latest statement from Selhurst Park indicates he will not be sold on the cheap.
Parish said: "He is an extraordinary talent. I said at the start of the season that keeping hold of Wilf would be like spending a lot of money on a transfer.
"Other sides can fly their kites but it would take £20million before we even got interested.
"He has got the lot, provided he keeps his feet on the ground and continues working so hard on his game - then it will all come."
The Nike Hypervenom is the latest cleat silo from Nike. It will change your game and is worn by the game's top players.
Neymar's move from Santos to Barcelona is no doubt the biggest summer transfer.
England will debut their new away jersey against Brazil at the Maracana Stadium on Sunday. Get in the Gear
Barcelona will wear this new home soccer jersey next season. They also have a new away jersey. Get them both.
Manchester City will try and win back the Premier League title with this new soccer jersey from Nike!
The adidas Nitrocharge is the most talked about new cleat in years. It was released on May 15 and will take your pitch by storm.
Germany is one of the top teams ever and they will play the US on Sunday.
The hoop soccer jersey is classic and cool. The USA hooped jersey is perfect for every fan. Get in the Gear.
The USA will wear their blue away jersey against Jamaica in their World Cup qualifier on Friday night.
Support the USA national team with an official 2013 Centennial soccer jersey from Nike. Its Official.