A GNSS ZTD enhancement framework integrating physical constraints and hybrid neural networks - Haojie Li; Qingzhi Zhao; Hongwu Guo; Anbang Wu; Ming Liu; Yibin Yao; Zhaoliang Zeng; Hong Liang; Qingyuan Guo; Yongjie Ma; Jiasong Tian; Zhaohui Xiong (Advances in Space Research, 2026)