Having missed last year's tournament with an ankle injury, Li comes into this year's tournament with literally everything to gain - and she got that campaign going with a 61 75 victory against Zheng.
Li looked headed for a much simpler straight set victory midway through the match, going up a set and a break at 61 21. Zheng fought back - she won three games in a row to lead 4-2 and, after Li caught up, held serve to get within a game of the set at 5-4. But the No.1-seeded Li shut that window quickly, holding at love to even it up at 5-5, then broke and held again to finish off the 65-minute second set.
It was Li's third straight win over Zheng, though Zheng still leads the overall head-to-head, 4-3.
"I'm happy with the result today, but I still feel I have so many things I can improve," Li said. "This was my first match since Doha three weeks ago, and I probably won't be 100% for my first match back.
"But I was happy I could at least learn some things from today's match."
And on her relationship with Zheng - a former Top 15 player and two-time Grand Slam semifinalist?
"There's always something special between us because we're from the same country, we played on the national team a couple of years, we've trained and eaten together - we know each other very well. But Zheng Jie and Peng Shuai are always the Chinese girls I'm playing - I wish we could have more.
"We had a lot of Chinese players in Melbourne this year, which was good for us."
Awaiting Li in the third round is Karolina Pliskova, who went on a mid-match tear to beat No.28 seed Klara Zakopalova, 75 62. Zakopalova was up 5-3 in the first set when Pliskova reeled off eight games in a row, saving a set point along the way and building a 75 40 lead. The Czech never looked back.
Li and Pliskova will be playing for the first time. Pliskova is 0-5 against Top 10 players.
Ivanovic had the most dramatic win of the bunch, not only rallying from a set down but also a break down in the second set and three times a break down in the third to beat Elina Svitolina, 46 75 76(1).