Nadal will begin his quest for a record 31st Masters title — but first in Paris — on Wednesday. The top-ranked Spaniard beat Chung in their only previous encounter on his way to a 10th title at the Barcelona Open in April.
Chung broke Zverev’s serve five times and saved the four break points he faced in a rout lasting less than one hour.
The last two spots for the season-ending ATP Finals in London will be decided in Paris, while Nadal is odds-on to end the year as No. 1 for the fourth time in his career.
David Goffin of Belgium and Pablo Carreno Busta of Spain are best placed to qualify for London, while Juan Martin del Potro needs to win here to make it. Frenchmen Jo-Wilfried Tsonga and Lucas Pouille, American Sam Querrey and U.S Open runner-up Kevin Anderson are in outside contention.
It is much more straightforward for Nadal to keep his top ranking.
He needs just one win to end the year as No. 1 ahead of Roger Federer, who pulled out of Paris after winning the Swiss Indoors in Basel for the eighth time on Sunday. Federer clinched his seventh title of the year, one more than Nadal, but is skipping Paris so he can stay fresh for London.
Nadal was “not happy” about pulling out of the Swiss Indoors, but felt he needed the rest after playing 75 matches this season, winning 65 of them.
By contrast, Federer has played only 53, winning 49. He has beaten Nadal four times this year, including in the Australian Open final.
“He takes his decision and he does it well,” Nadal said on Monday of Federer’s decision to stagger his tournaments. “It (has) worked very well for him.”
After their five-set thriller in Melbourne, Federer did not drop a set against Nadal in the next three wins.
Also in the first round on Monday, there were wins for Frenchmen Richard Gasquet, Jeremy Chardy, Nicolas Mahut and Julien Benneteau. Also through were Filip Krajinovic of Serbia, Peter Gojowczyk of Germany, and Robin Haase of the Netherlands.
Benneteau beat Denis Shapovalov of Canada 6-4, 6-4 and next plays Tsonga, while Mahut had a tougher time against another Canadian, Vasek Pospisil, 5-7, 7-5, 76 (4). Gasquet beat Paire for the fifth straight time; and Chardy dispatched countryman Gilles Simon 6-3, 6-0.