She credited her love of dancing for helping keep training fun after an erratic performance.
After becoming frustrated with her error count on Rod Laver Arena, the 23-time Grand Slam champion was in a much lighter mood after organisers played a viral video of her performing a vibrant hip-hop routine during her post-match interview.
"I always dance. I'm not the best dancer, but I love dance," Williams said.
"It's nice and fun to do. It's different. It's better than just going to the gym every day."
The video, which first made its way online in November, also featured American teenage sensation Coco Gauff who spent time training with compatriot Williams during the off-season.
The 15-year-old is in the same half of the draw as Williams and they could be set for a quarterfinal clash at Melbourne Park after Gauff reached the third round earlier yesterday.
"I think she [Gauff] has a good chance to keep winning. She's a fighter. I have to do what I do, play everyone at every point, so we'll see," Williams said.
The 38-year-old, who is bidding for a record-equalling 24th major title, was dominant in the first set against Zidansek, wrapping up the opener in just over half an hour.
But the 70th-ranked Slovenian defended impressively in the second set, saving seven break points as Williams racked up the mistakes, ending the match with 28 unforced errors.
Zidansek, however, could not keep up the resistance and Williams clinched victory with a cross-court forehand winner to set up a meeting with China's Wang Qiang.
Looking ahead, Williams said she hoped to play at the Tokyo Olympics in July, but acknowledged stiff competition with seven US women vying for four available Games' berths.
"Yeah, it's a lot of Americans," she said. "We'll see. Hopefully I can make it. If not, it's not the end of the world. I've played a lot of Olympics, so it will be good."
