The newly promoted club and Roy Hodgson's side will battle each other in Saturday's league match at the Craven Cottage.
Pape Souare, Cheikhou Kouyate, Jeffrey Schlupp, Jordan Ayew and Zaha could feature for the South London side while Jean Michael Seri, Floyd Ayite, Neeskens Kebano, Andre-Zambo Anguissa could make their Premier League debuts for the Whites.
However, Merson disclosed that the Ivorian's form would be the difference after the club fend off interests for their prized asset in the transfer market.
The Eagles failed to claim a point in Zaha's absence last season and his importance to the team was boldly stated with nine goals in 29 league games last term.
"It all depends on how Wilfried Zaha performs as he makes all the difference. I don't think they won a football game without him last year, so Palace will have done well to keep hold of him," Merson wrote in his SkySports column.
"This is a real benchmark for Fulham early on, playing a team that struggled last season but are better than what they were."
The former Arsenal midfielder went on to predict stalemate at Craven Cottage despite picking Roy Hodgson's men as likely winners of the encounter.
"I'm going to go for a draw, but if I had to pick a winner it would be Palace," he added.