In that case, the time is really pressing for you. As the train Z9 arrives at Hangzhou train station while the train D377 to Yandangshan departs at South train station in Xiaoshan area. And it takes around 35min by taxi between the two stations. Personally, you would better choose to take some trains later such as D3203 leaving at 12:18. You can buy the tickets at the train station directly after you reach Hangzhou.