Two-time former champion Van Gerwen was aiming to make it a hat-trick of triumphs in Blackpool, but he was sent packing by giantkiller De Zwaan 10-6 in the opening round.
World No 68 De Zwaan claimed a famous victory when they met in the UK Open earlier this year and he sealed a sensational double over his fellow countryman at the famous Winter Gardens.
“I really don’t believe it, I played really well and the confidence was there,” De Zwaan told Sky Sports.
“I said to myself, ‘keep going, keep pushing’. I just wanted to play my game and see what happens.”
Van Gerwen, who crashed out at the quarter-final stage here last year, had De Zwaan hanging on to his coattails at 5-5.
The 29-year-old hit a ton finish to hold throw, but De Zwaan responded with a cool 121 before nailing D19 for an 8-6 lead.
De Zwaan hit tops to win the next leg and he held his nerve to hit D16 and complete a stunning victory.
Only two-time winner Van Gerwen and 2007 champion James Wade have previously tasted victory at the historic Winter Gardens from this year’s 32-player field – but Dutchman’s defeat has blown the tournament wide open.
De Zwaan will next take on 2013 finalist Adrian Lewis after he battled back to defeat James Wilson 10-7.
Lewis, who picked up the 16th seeding after moving back up the rankings this year, came good against Huddersfield thrower Wilson after looking on the verge of an early exit.
The Stoke-on-Trent thrower was pegged back to 2-2 before he landed a showstopping double top, double top finish to take out a ton.
All looked positive for Lewis until Wilson hit back with an 86 checkout to break again and he soon won his fifth leg on the spin with D8 to move 7-3 up. Lewis stopped the rot with a neat 82 finish, while Wilson, nicknamed ‘Lethal Biscuit’ crumbled under pressure.
‘Jackpot’ won seven out of the next eight legs, finishing the contest with a stunning 116 to set up the dream match with Van Gerwen.
“I’ve got the courage, I’ve always got the belief, just sometimes my mindset is not always there,” Lewis admitted. “Van Gerwen is the number one and he has been the best player in the world for the last three or four years so it will be an honour [to play him] and I’ll be looking forward to it.”
Premier League finalist Michael Smith starts his Blackpool challenge against in-form Jonny Clayton with the winner set to face Dave Chisnall.
Four-time quarter-finalist Chisnall produced a 63 per cent checkout success rate to dump out former World Youth Champion Keegan Brown.
‘Chizzy’ sunk a 148 in the sixth leg before landing a majestic 147 in the next to take a 4-3 lead. He then stepped on the afterburners to complete a comprehensive 10-4 win.
The prestigious event sees 32 players competing for £500,000 in prize money, including a first prize of £115,000 for the winner along with the newly-titled Phil Taylor Trophy.
Join us for further coverage of the World Matchplay, when 16-time champion Phil Taylor will be with part of the Sky Sports team on Sunday, July 22 for a double session of tungsten at 1pm & 7.30pm on Sky Sports Action. The darts will run through to the final on Sunday, July 29.