As dreadful as Leicester were, Palace were excellent, clinical and composed. Zaha was - as always - influential in the victory, and the slightly inconsistent Andros Townsend and Ruben Loftus-Cheek both stood out.
After a long, difficult season, we can finally relax. Mathematically we are not safe from relegation yet, but for all intents and purposes relegation seems extremely improbable.
The real game changer was the red card for Marc Albrighton. As with so many players in the Premier League, the Foxes' make-shift right-back failed to cope with Zaha and his pace, so made the decision to pull him down when through on goal.
That subsequently robbed Leicester of their best player at a point where all three subs had been used. At 2-0 down, it was already game over.
But Palace were in no mood to rest on their laurels and Ruben Loftus-Cheek expertly added a third by dummying Ben Hamer and rounding the keeper, with Mamadou Sakho channelling his inner Kevin de Bruyne to play a glorious through ball to the Chelsea loanee.
Then Patrick van Aanholt coolly slotted home after Jeffrey Schlupp was denied.
But the best was saved for last. With two minutes remaining, substitute Christian Benteke was taken out in the penalty area by Harry Maguire.
The instructions from the bench were for Luka Milivojevic to allow Benteke to take the spot kick, in a complete role-reversal of the debacle at home to Bournemouth earlier in the season.
The Belgian striker slipped as he took the kick but it sailed past Hamer into the net. “Ooh Christian Benteke” rang around Selhurst Park as all 10 outfield players embraced with Benteke after what was only his third goal this season.
This was a comprehensive win, and it was very much deserved. Leicester looked like they wanted the season to be over and done with weeks ago, and we are now up to 11th with struggling Stoke and West Brom to play.
We could somehow finish in the top half of the table, despite giving the rest of the league a seven-game head start. Sir Roy Hodgson, the borough of Roydon.
Van Aanholt revival
The Dutch left-back was roundly criticised for some terrible performances in the opening months of the season, and rightly so.
But since Christmas he has morphed into a new player, becoming most probably the most effective and consistent performer this calendar year.
Yes Zaha is superb, but Van Aanholt has hardly put a foot wrong. Against the Foxes he earned his reward by netting the fourth goal, and putting in yet another stylish performance in defence.
Both defensively and offensively he has been a significant contributor to our recent success and has undoubtedly earned himself the right to keep the shirt next season.
The 5-0 scoreline saw Palace equal their biggest ever top-flight victory.
The previous largest victory was also a 5-0 win, back in 1972 as Don Rogers inspired us to smash Manchester United at Selhurst. Not bad.