From Changsha you have 2 overnight trains going direct to Zhangjiajie (02:18 and 03:36/ K536; T8316)
If you leave Nanjing South 15:28 you arrive at Changsha South 21:36 (G 1483).
Or you take the 1st train (G579) from Nanjing at 08:02 in the morning, be in Changsha at 12:52 and take the long distance bus to Zhangjiajie.
Sitting around 5 hours in the night isn't so comfortable. Is there really a bus from Changsha to Zhangjiajie? I was a couple of years ago in Zhangjiajie and traveled to Nanchang from there. It was necessary to get to Changde by bus, then by train to Changsha. But is there is a bus to Changsha we will take that, thank you!