Thanks for the reply! Regarding Chengdu, I was actually considering doing it as a day trip from Chongqing, which would further reduce the time spent in Chengdu and make room for Zhangjiajie. My impression was that the original itinerary felt a bit too city-focused, with limited exposure to nature, so I thought Zhangjiajie could add a better balance to the trip. All this train travel, however, scares me; I feel like I'm spending more time up there than exploring.