Zverev, who is the tournament favourite after Spanish top seed and World No. 2 Rafael Nadal withdrew due to a lingering hip injury, earned an early break in Tuesday night's match to go up 3-1 and held serve the rest of the way to wrap up the first set, reports Efe.
In the second set, McDonald, who was a last-minute replacement for American Steve Johnson, managed to stay on serve until 5-5 but Zverev reeled off eight straight points to take the match in an hour and 20 minutes.
Zverev's serve was the key to his victory, as he won nearly 80 percent of his first-serve points and 70 percent of his second-serve points and saved the lone break point he faced.
Next up for the 20-year-old Zverev in Wednesday's round of 16 will be Germany's Peter Gojowczyk, who cruised past Mexican wild card Lucas Gomez 6-3, 6-2 on Tuesday.
In other Acapulco action, two of tennis' other promising young stars, 24-year-old Austrian Dominic Thiem and 18-year-old Canadian Denis Shapovalov, set up a much-anticipated round-of-16 clash with victories on Tuesday.
The third-seeded Thiem clawed out a 6-3, 5-7, 7-5 victory over Cameron Norrie of the United Kingdom, while Shapovalov rallied for a 6-7 (3-7), 6-3, 6-1 win over Japan's Kei Nishikori, a former top-five player who is making his way back after suffering a season-ending wrist injury in 2017.
In women's singles action on Tuesday, American top seed Sloane Stephens, the reigning US Open champion, easily defeated France's Pauline Parmentier 6-4, 6-0.
(This story has not been edited by Social News XYZ staff and is auto-generated from a syndicated feed.)
This website uses cookies.