Overlord wrote:BTW Zhang did not learn from Wu Mengxia.
What I heard through the grapevine is that although Zhang did study under Gao Yisheng, he actually got more instruction from his close friend Wu Mengxia. One of the reasons being that the fees Gao charged, especially for combat applications, were quite high.
Direct evidence suggesting that Zhang learned from Wu, or that the two compared notes at the very least, is that both of their systems include and emphasize the heavenly stems (Tiengan) exercises in basic power training. (In Gao's original system, Tiengan is only used to refer to the pre-heaven palms.)
AFAIK, Tiengan exercises are only found in Zhang and Wu's branches of Gao Bagua, and are most likely Wu's own invention or something he obtained from another source. It's unsurprising considering that Wu had already learned from a number of Xingyi and Bagua teachers prior to becoming Gao's student.