Halep needed just 76 minutes on the main stadium court to dispatch her practice partner Wang as she won 64 percent of her first-serve points and broke Wang's serve seven times.
Juan Martin del Potro beat Spaniard David Ferrer 6-4 7-6 (6-3) and will play fellow Argentine Leonardo Mayer, who defeated Japan's Taro Daniel 6-4 6-1.
"I am confident. I am feeling the game", she said.
Although Halep's own performance was far from faultless, particularly in the first set, the Romanian triumphed 7-5 6-1 and will now face Petra Martic in the last eight.
Wozniacki takes the court in Indian Wells later in the day when she faces 20th seeded Russian Daria Kasatkina. Despite several top players seeing upsets already, there is a lot of competition left at the WTA Tour event.
Part of Halep's preparation for Indian Wells included hitting balls with Wang.
If Wang was high on confidence following her performances earlier in the tournament, her morale was surely raised further as she twice responded immediately to falling a break down in set one.More news: UConn is top seed in women's tourney
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"It was really important, because he just told me what I have to do".
"I knew it would be like that because we practised a few days ago and she beat me in practice", Halep said. "I did exactly what he said after that".
No. 5 seed Karolina Pliskova and the waiting-to-break-out Naomi Osaka set up a quarterfinal meeting when Osaka beat Greece's Maria Sakkari 6-1, 5-7, 6-1, and Pliskova stopped the run of 16-year-old American wildcard Amanda Anisimova 6-1, 7-6 (2). It was the first time Venus has beaten Serena since 2014 in Montreal.
She and Serena usually meet later in the draw in the semis or the championship match.
"It was not an easy match to figure out". "She has everything in her game". "And it was a quick comeback from yesterday, where you have the emotions of, 'Hey, this feels like a final [against Serena]!' But guess what, you're only in the fourth round".
Williams, who is the oldest female player in the draw at 37, rallied back in the second set to book her spot in the quarter-finals.
Williams next faces Carla Suarez Navarro of Spain who rolled past Danielle Collins 6-2, 6-4.