The 1-0 defeat made it an unhappy return to Selhurst Park for ex-Eagles manager Roy Hodgson.
The Hornets already needed a miracle to survive but it was old nemesis Zaha who had the decisive say to ensure his former manager Roy Hodgson endured an unhappy return to south London.
Hodgson, who received a CBE at Buckingham Palace in midweek, saw his 19th-placed side struggle throughout and defeat confirmed they will be back in the Sky Bet Championship next season with Hassane Kamara also sent off to further blight a bad day for the club.
Defeat at home to Burnley last weekend had virtually confirmed the Hornets’ instant return to the second tier, which meant the veteran manager went back to his previous stomping ground on a sour note.
It was last May when the ex-England boss revealed his intention to walk away from management for good and while a reduced crowd of 6,500 spectators – due to coronavirus restrictions – bid farewell to him in a 3-1 loss to Arsenal at the end of last season, this occasion at least enabled the 74-year-old to take in a sold-out Selhurst Park for one final time.
A fine reception greeted Hodgson as he walked to the away dugout but the Eagles were not so generous on the pitch with Marc Guehi and Michael Olise going close for the hosts in the opening exchanges.
Eventually the pressure told in south London but the deadlock was only broken after 31 minutes from the penalty spot
When Olise headed Ebere Eze’s cross onto the hand of Kamara, referee Graham Scott was left with the easy task of pointing to the spot. VAR reviewed the incident to check if the protests of the left-back – who insisted Olise had pushed him – were justified but the decision remained.
It gave Zaha, who has plenty of history with Watford and was once teased by their mascot Harry the Hornet, the chance to inflict more pain on the visitors and he fired home the penalty for his 14th goal of the season to leave the away side on the brink.
Ben Foster kept the deficit at one with excellent saves to deny Guehi’s header and Olise from close-range following a wonderful team move before half-time.
The Hornets and in particular Joshua King came out with better intent after the break with the forward able to force Palace’s back-up goalkeeper Jack Butland into action for the first time in the 49th minute, but his effort was weak after an impressive dibble.
Normal service soon resumed and Odsonne Edouard was unlucky not to double Palace’s lead just past the hour mark when he beat three players with a step-over and saw his low strike nutmeg Foster but hit the far post.
Despite the writing being on the wall, the visiting support remained in fine voice and joined the Palace faithful in mocking their own plight.
Hodgson’s misery increased with 22 minutes left when Kamara received a second yellow card from referee Scott for a foul on Olise and was waved off down the touchline by the Palace fans.
Substitute Jean-Philippe Mateta could have added a late second for the hosts but Foster produced another excellent save to thwart his header before he also denied Jeffrey Schlupp in stoppage-time.
The match had the feel of a pre-season friendly now and eventually Watford’s suffering came to an end. There was still time for Hodgson to receive another ovation but it was the latest day to forget for the Hornets in a bad season.