Zhoushan do not have train station at all, as I know. You should get to Hangzhou or Ningbo first and then shift trains to Beijing. Dinghai is about 2.5-3 hours from Ningbo. I think you should get to Ningbo. NIngbo Train Station has Z10 to Beijing leaving at 15:32 and getting to Beijing Railway Station 15 hours later. There is only one train. If you can not make it, you should choose Hangzhou as the transfer station. The last train to Beijing from Hangzhou leaves at 22:58.