Zaha wants out of Crystal Palace and is desperate to join Arsenal.
The Ivory Coast international is keen to prove himself at an elite club – but Palace have no intention of letting him go on the cheap.
They want a sky-high fee of around £80m for their academy graduate.
And that major valuation means a deal could yet collapse before the 5pm transfer deadline on August 8.
Sky Sports reporter Dharmesh Sheth issued an update on the latest episode of the Transfer Talk podcast.
He said: “At the beginning of the window, from the sources we were talking to there was quite a confidence that Wilfried Zaha to Arsenal would happen.
“There were the quotes from his brother that put it into the open – it was his dream to play for Arsenal, that sort of thing.
“But the latest it’s gone on you’re thinking to yourself, are Arsenal going to be able to afford this because Palace are not budging on this.
“One source I spoke to yesterday described the possibility of Zaha going to Arsenal as just 50/50.
“So from it being an increased confidence at the beginning of the window, it looks like it’s going slightly lower as we go towards deadline day on this one.”
Zaha’s desire to join Arsenal was revealed by his brother, Juicael, earlier this summer.
“Wilfried will always hold Crystal Palace and their fans in the highest regard and all the support they have given means the world to him,” he said.
“It’s my brother’s dream though, to play for Arsenal.
“Given all that Wilfried has given to Crystal Palace to help them remain a Premier League club, I hope Palace will be able to see their way to agreeing a deal with Arsenal that allows Wilfried to realise his dream of playing European Football for the club he’s supported since childhood.”