"I am still in dreamland, this week keeps getting better and better for me," said De Zwaan, who at world number 68 was the lowest ranked player at the start of the tournament. Every game I feel more confident, I feel like I can beat anyone.
"I'm going to celebrate this win and then prepare for the rest of the tournament - I believe I can win this title."
He will be underdog once again in the semi-finals when he comes up against nine-dart hero Gary Anderson, who nailed a perfect leg in an astonishing 19-17 victory over Joe Cullen.
Despite his heroics in the fourth leg of the match, the Flying Scotsman was taken the distance by the plucky Rockstar, who raised the Winter Gardens roof himself with his second 170 checkout of the tournament to go 10-9 up.
Cullen spurned two match darts in one of the most gripping contests ever seen on TV but in the end it was Anderson who maintained his dream of winning the first World Matchplay title of his career.
CLICK HERE FOR MORE FROM GARY ANDERSON'S EPIC QUARER-FINAL VICTORY
Thursday July 26
Quarter-Finals (Best of 31 legs)
Friday July 27 (1900 BST)
Quarter-Finals (Best of 31 legs)
TV Channel: Sky Sports
CLICK HERE FOR WORLD MATCHPLAY DRAW, SCHEDULE & RESULTS