I want to travel to Zhangjiagang city from Beijing, what’s the best route? Flight or train? Options?

No train station is available in Zhangjiagang. From Beijing, you could take a high-speed train to Suzhou first and then take a bus to Zhangjiagang. Or, you could take a flight to Shanghai first and then to Zhangjiaggang. And the first transport route will be better.