Shan was the main threat on Zhejiang's offensive end, constantly burying three-pointers and driving to the basket. She scored nine points in a 10-minute stretch as Zhejiang raced ahead 45-33 at the half.
With the result, Union Berlin move up to third place in the standings, while Mainz stay 17th after suffering their third straight defeat of the new season.
Elsewhere, Eintracht Frankfurt came from behind to beat Hoffenheim 2-1. Borussia Monchengladbach wrapped its first victory of the campaign after easing 3-1 past rival Cologne. Wasteful Bayer Leverkusen shared the spoils with newly-promoted Stuttgart following a 1-1 draw and Leonardo Bittencourt's sole goal of the match helped Werder Bremen to edge newcomer Armenia Bielefeld. Enditem
"We didn't perform well in the first quarter. We had a tough start, but ultimately took our chance," Shaanxi coach Jiang E'Ying reflected.
The 33-year-old will play 17th seed Pablo Carreno Busta the round of eight. The Spaniard dispatched German qualifier Daniel Altmaier 6-2, 7-5, 6-2.
Boulaye Dia levelled in the 66th minute to clinch the second point for Reims this season.
Shandong began to lose momentum after the interval, and Inner Mongolia scored many fast break points on turnovers. With a 30-point margin in hand before the last 10 minutes, Inner Mongolia met little challenge thereafter.
Beijing closed the first quarter on a 17-4 run, going up 33-17 as the quarter time ran out.
Julian Draxler, Idrissa Gueye and Kylian Mbappe added another three in the second half while Angers pulled one back in the 52nd minute.
In her WCBA debut, Fang displayed impressive speed and sharpness on the offensive end, but due to a lack of experience, she was called two offensive fouls in a row when the two sides were involved in jigsaw-like contention in the third quarter.
Kvitova went into the match quickly as she broke her Chinese opponent twice to surge to a 4-0 lead in the opening set, before serving for the set in the eighth game.