And he underlined his status as the man to beat in Shanghai as he battered the Italian Fognini 6-3, 6-1.
Del Potro will John Isner of the US or Viktor Troicki of Serbia in the last eight on Friday.
In the quarterfinals, Nadal will play sixth-seeded Grigor Dimitrov of Bulgaria, who got past Sam Querrey of the USA 6-3, 7-6 (3).
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Michel Barnier said that despite the "constructive spirit" shown in this week's fifth round of talks, "we haven't made any great steps forward".
However, there is a determined look in the eye of the 29-year-old and a first title of the year would send him soaring up to 12th.
The 46th-ranked Harrison led 4-2 in the third set and then 6-3 in the tiebreaker.
Third seed Zverev was a different matter, though, and, after losing the first four games, Bedene accepted he would not be able to compete and shook hands.
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Republican Senator Rand Paul advocated for this solution when the discussions for the replacement of the Obamacare was discussed. Trump first vowed late last month to take executive action to fix aspects of the law, which he has deemed a failure.
It was del Potro's only break of serve for the match as the world No.23 held strong to close out the match five games later.
A fan at least came away with a demolished racquet for a souvenir after the young German handed it to a spectator.
The 20-year-old Zverev, who has collected 5 ATP World Tour titles this season, lost his temper when broken by the Argentine at 2-2 in the decider and flung his racquet down to the ground, reports Xinhua news agency. "I'm a bit pissed off because I feel like I played well and that's the upsetting part of it - I could have done great in this tournament".
Southwest to begin flying to Hawaii
But Watterson refuted the notion that Southwest won't be able to offer lower fares. "We anticipate fares will drop", he said. Chairman and CEO Gary Kelly said the destination is a request the company has received for years.
Fourth-seeded Marin Cilic will face Albert Ramos-Vinolas of Spain.