There are about three D trains (bullet trains) running from Shanghai to Zhengzhou. However, they are different from the newly opened G trains from Zhengzhou to Xian. Both D trains and G trains have a few stops. However, the speed for the G trains can reach 350km/h. For the details, you can refer to the page about the train types: https://www.travelchinaguide.com/china-trains/types.htm