The top-seeded Jankovic beat Aleksandra Wozniak 6-3, 7-5 in the second round Wednesday, leaving her on course to threaten Serena Williams' hold on the top spot in women's tennis.
Jankovic can't overtake Williams this week - even if she wins Sunday's final - but it could happen next week when the two meet in Stuttgart where eight of the top 10 women are scheduled to play.
Jankovic can reach 4,070 points by winning this tournament, just 21 short of Williams.
Zheng reached the second round Wednesday, beating Agnieska Radwanska of Poland 6-2, 6-3. She's the only local woman to do so after the four others disappointed home fans with first-round losses.
Jankovic had some trouble with the Canadian, needing 35 minutes in the first set on a chilly, damp night on the outdoor courts at Beijing Tennis Center. She struggled in the second set, changing to warmer clothes late in a match that wrapped up a day delayed four hours by early rain.
In the past three months, Zheng has reached the Wimbledon semifinals and claimed the Olympic bronze medal in doubles with Yan Zi. But beating Radwanska might matter just as much - both to fans and sponsors trying to establish a tennis base in China.
"I felt as a Chinese player in an event in China, I should perform well,'' she said. "This is very important for me.''
Zheng reached the semifinals last week in a WTA event in Guangzhou in southern China, but caught a cold in the process.
"I actually thought about withdrawing, but the China Open is in my homeland so I thought I should stay and keep trying,'' she said.
The four other Chinese women in the first round all lost Monday. Fortunately for Zheng, her match was delayed a day due to rain, which allowed her to shake off a fever. She also got another break when rain delayed the start of play by four hours.
Zheng became a national heroine, saying after her Wimbledon success that she would donate her winnings in England to help survivors of the May 12 Sichuan earthquake that killed almost 70,000.
Zheng is from the Sichuan city of Chengdu, but she's not had time to return home.
"As a professional player, I should finish my season first,'' Zheng said. "I have a few events after this and then I plan to go back and see what I can do for them.''
In a key second-round match, No. 7 Daniela Hantuchova outlasted Tamarine Tanasugarn 6-1, 0-6, 7-5.
The China Open is a men's and women's event.
The top-seeded David Ferrer and No. 2 Andy Roddick play second-round matches Thursday. Both received byes. Ferrer plays Dudi Sela of Israel and Roddick faces Brendan Evans in an all-American match.
On Wednesday, No. 8 Sam Querrey defeated Jesse Levine 1-6, 6-2, 7-6 (4) in another all-American match. Also, Ivo Minar of the Czech Republic beat Lee Hyung-taik of South Korea 6-3, 3-6, 6-2; Sela defeated Nicolas Devilder of France 6-4, 6-3; and Jean-Claude Scherrer of Switzerland beat Peng Sun of China 6-4, 7-6 (7).
Also, Fernando Verdasco of Spain beat Bobby Reynolds of the United States 6-3, 6-3; Go Soeda of Japan defeated Bai Yan of China 6-4, 7-5; and Brendan Evans of the United States downed Roko Karanusic of Croatia 7-6 (5), 1-6, 7-6 (10).
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