Zhang, who picked up her first WTA title last Saturday in Guangzhou, moved over to Ningbo and dropped only three games in a first-round win and then two in beating Zheng in the second round.
Zhang took more than 60 percent of the points off Zheng's serve and finished off six of her 10 break chances.
Johanna Larsson also ousted a high seed, posting a 6-0, 7-6 (7-2) decision over No. 3 Lourdes Dominguez Lino. Larsson won all but seven points in the first set and survived the only break she suffered in the second set for the win.
No. 1-seeded Bojana Jovanovski advanced in a walkover against Shahar Peer. Jovanovski next goes against Anna Schmiedlova, who disposed of Vesna Dolonc 6-0, 6-1 by taking nearly two-thirds of the points in the match.
Fourth-seeded Yvonne Meusburger took out Petra Cetkovska 6-2, 6-1 and seventh-seeded Yaroslava Shvedova outlasted Zheng Saisai 4-6, 7-5, 7-0 in other matches Tuesday involving seeded players.
Also Tuesday as the second round was completed, Johanna Konta rolled by Katarzyna Piter 6-1, 6-1 and Anabel Medina Garrigues beat Alexandra Dulgheru 6-2, 6-4.