(Peskin and Schroeder) Numerator of vertex correction

[ndcat10]

Hi I am studying qft with worldwidely used text, written by Peskin and Schroeder, An introduction to qft. I have trouble with the calculation of thr numerator on pp. 192. I got additional term $2m(z-xy)(mγ^μ - p^μ)$ between spinors, which seems not vanishing. Is there any idea to treat this problem? Thanks in advance

 

[ndcat10]

The problem is solved. Maybe I made mistake somewhere.(I calculated hundreds times to exaggerate.) Anyway thanks for reading this annoying post(at least I think I made another trash, but more than 100 people read this)