Next up for Williams is No.25 seed Alizé Cornet, who had to grind hard to get past the hard-hitting Petra Cetkovska, 6-4, 5-7, 6-3. Cornet beat Williams in their last meeting in Dubai this year.
"She does everything well - that's why she was able to get a good win off of me," Williams said of Cornet. "And she never gives up - she's a really big fighter, and she gets a lot of balls back.
"But I'm ready. It's time for me to step up my game and do what I know I can do."
Sharapova isn't worried at all about her quick matches thus far - for a very real reason, too.
"I had four three set matches in a row at Roland Garros," the former World No.1 commented.
"It was quite a long battle, so I'm going to take these as much as I can get them!"
Williams and Sharapova are two wins away from an absolutely mouthwatering quarterfinal clash.
Elsewhere, some mouthwatering third round match-ups were set up, most notably No.11 seed Ana Ivanovic against No.19 seed Sabine Lisicki, after Ivanovic cruised past former Wimbledon semifinalist Zheng Jie, 6-4, 6-0, and Lisicki beat Karolina Pliskova, 6-3, 7-5, in a battle of the big servers.
Ivanovic beat Lisicki in the pair's only previous meeting, in Stuttgart this year. But obviously the German is much more dangerous on these courts - she's been to the quarterfinals or better in all of her last four appearances here, of course reaching her first Grand Slam final here a year ago.
Another tantalizing third round match-up that came to fruition was No.13 seed Eugenie Bouchard against No.20 seed Andrea Petkovic, after Bouchard beat Spanish wildcard Sílvia Soler-Espinosa, 7-5, 6-1, and Petkovic got past Irina-Camelia Begu, 6-4, 3-6, 6-1. Petkovic is 3-0 lifetime against Bouchard.
WTA Rising Stars Madison Keys, Alison Riske and Zarina Diyas were also among the winners, with Keys battling past No.31 seed Klara Koukalova, 7-5, 6-7(3), 6-2, and Diyas pulling off an even bigger upset, toughing out a 7-6(12), 5-7, 6-2 grinder against the No.15 seed, Carla Suárez Navarro.
Zvonareva, a two-time Grand Slam finalist and former World No.2, has been trying to rebuild her career this year after missing a year and a half of action due to illness and a shoulder injury. This is the first time she's won back-to-back matches in her comeback - could this be the start of something big?