Two countries boast multiple qualifiers, with trio of Americans featuring in the four groups.
Keys, the No.3 seed, is joined by No.2 seed Sofia Kenin and No.7 seed Alison Riske, who were both drawn into the Camellia Group.
They are placed there by No.11 seed Karolina Muchova, winner of the Seoul Open, who saw her spot confirmed by virtue of Anastasia Pavlyuchenkova's defeat to Belinda Bencic in the final of the VTB Kremlin Cup.
Croatia also boasts two representiatives, with Vekic being joined by No.5 seed Petra Martic, who landed with Keys in the Orchid Group.
The field is rounded out by Chinese No.2 Zheng, the San Jose champion. The 25-year-old home favorite won her first title at the Premier event during the US Open Series this summer beating Sabalenka in the final, and rounds out the Orchid group.
"In San Jose, I actually played three players who are also going to be here and that definitely gives me confidence and the most importantly I've been improving myself along the way," Zheng, who was also a wildcard in her first appearance in 2015, said.
"In Zhuhai in 2015 was the first session here and at the time I was just up on the journey as a professional player. I have come a long way. My performance is much better than before in 2015, but I've been through a lot of things like injuries and surgeries and so I feel a lot in this journey.
"No one is an easy player, so every match is going to be a tough match. It's really depending upon how you put it out on the court and that will make the difference as far as a win or a loss. I'm looking forward to all the challenges."