Hi, I want to visit my friends to Wuhan from Zhengzhou, is there any direct bus and how ling it take

there are direct buses from ZZ Central Bus Station to Wuhan, and the duration is about 7.3 hours. There are two every day at 10:30 and 18:30.
Actually, you can also choose to take a bullet train to Wuhan in around two to three hours. You can search for more detail trains information on this website.