how i can reach from zhengzhou airport to ZZ medical university by bus

I think you may mean the Medical School of ZZ University, right?
If so, I think from the airport, you can take the airport shuttle bus to reach the local railway station and then take a taxi to reach the ZZ University (South Campus). Then you can find the school shuttle bus to reach the Medical School.
If you want to reach the Medical school directly, you can take a taxi to reach that school directly from the local railway station. It may be hard for you to transfer the local public buses.