In set two, Williams broke serve at 2 all to lead 3-2 before winning the final three games of the set as well.
On serve but trailing in the final set at 6-7, the American hit two consecutive aces to open the game. A Zheng forehand return down the line wide followed by Williams’ 23rd and final ace of the day- down the tee; leveled the set at 7 all.
With Williams’ level of play at a new high, Zheng hit an inside out forehand down the line wide on breakpoint to fall behind 7-8.
On matchpont, a Williams crosscourt backhand volley winner would end the encounter after more than two hours of play.
For the match, Williams converted 3 of 5 breakpoints; while Zheng went 0 of 6.
“It’s a tough match, because she has big serve,” Zheng said. “It’s very difficult against her on the grass court.”
Williams hit 54 winners to 24 unforced errors.
In the fourth round Monday, Williams meets the unseeded Yaroslava Shvedova of Kazakhstan. The American took the pair’s only previous meeting 6-3, 6-2 on a hardcourt in Toronto in 2009. Monday in the USA, ESPN and ESPN2 will both provide live Wimbledon television coverage concurrently throughout the day.
Williams won the Wimbledon singles title in 2002, 2003, 2009 and 2010 and topped the WTA Tour rankings before foot and lung medical complications in late 2010 and early 2011 would result in a several months long injury break from the tour.
The American could not meet the French Open champion and world number one Maria Sharapova of Russia until Saturday’s final round.