Peng broke Han Xinyun's serve six times and was 19 of 24 on her opponents' second serve in her 6-1, 6-3 triumph.
"It was not in my original plan to play Nanchang, but I'm glad I came," Peng said. "Nanchang has changed a lot from my last visit years ago, and it is very beautiful. I'm still getting used to the courts here, but I think I'll get better with each match."
In another all-Chinese match-up, 18-year-old World No.422 Liu Fangzhou staged a mini-rally down 4-2 in the first set against World No.59 Zheng to win it in a tie-break. Then after Liu went up 2-0 in the second set, Zheng retired with a right foot blister, handing Liu her first Top 100 win.
"I'm very happy that I won today," Liu said. "The thought of being able to beat Zheng Jie had never occurred to me! It means a lot. I just played my game and fought for every point and every game."
Mrdeza fought off three set points in the first set tie-break and for the match was five of six on break points and 17 of 22 on second serve return points.
Zhang also overcame a set point against her in a first set that lasted one hour and 12 minutes.
Also, No.3 seed Misaki Doi beat Dalila Jakupovic, 6-3, 7-6(4), and No.6 seed Zheng Saisai snapped a five-match losing streak with a 2-6, 6-1, 6-3 defeat of Michaela Honcova, who lost despite converting on all six of her break points.
In a match involving unseeded players, Marina Melnikova rallied from a 5-2 third set deficit and survived a match point at 5-4 en route to a 6-2, 4-6, 7-5 victory over Gioia Barbieri.