AZ were surprisingly beaten by Roda JC on Saturday, meaning a convincing victory for Steve McClaren's side 24 hours later put the sides level on 39 points and comfortably ahead on goals.
De Jong scored twice in the opening 23 minutes to put his team in control at the interval, adding his third after Virgil van Dijk threatened to bring the visitors back into it with his 47th-minute effort. Leroy Fer completed the scoring in the 67th minute.
John Guidetti also bagged a treble as Feyenoord beat defending champions Ajax 4-2 at De Kuip.
Feyenoord have been very much in the shadow of their rivals in recent years but they were 2-1 up at the break as Guidetti struck twice, including one from the spot, to cancel out Christian Eriksen's opener.
Otman Bakkal extended the lead five minutes after the break before Dmitry Bulykin pulled one back 10 minutes from the end, but on-loan Manchester City striker Guidetti struck again three minutes later to steal the headlines.
Elsewhere, Lasse Schone scored twice, including one from the spot, as NEC Nijmegen beat ADO Den Haag 2-0, while RKC Waalwijk were 4-0 winners over VVV-Venlo.
Evander Sno, with a 29th-minute penalty, Frank van Mosselveld (31), Robert Braber (80) and Rick Ten Voorde (90) were on target for the hosts.
