quantum field theory - Is there a mistake in a QFT textbook? - Physics Stack Exchange

I tried to calculate one of the problems in the textbook Gauge Theory of Elementary Particle Physics by Ta-Pei Cheng and Ling-Fong Li. On page 248 you can find the following calculation of a loop

Quantum Field Theory: A Modern Introduction: Kaku, Michio: 9780195076523: : Books

quantum mechanics - How does an electron wave move between locations in QFT? - Physics Stack Exchange

quantum field theory - Electron Positron annihilation Feynman Diagram - Physics Stack Exchange

quantum field theory - $γγh$ interaction in the Standard Model - Physics Stack Exchange

Show that time derivative of creation-annihilation operators of Klein-Gordon field are zero - Physics Stack Exchange

Quantum Field Theory, as Simply as Possible: Zee, Anthony: 9780691174297: : Books

What are some of the books on quantum chromodynamics (QCD) that require no prior knowledge of string theory or particle physics? - Quora

Theories and their domains of applicability?

quantum field theory - What is the missing part of the argument needed to justify the claim of (2.52) in Peskin and Schroeder's QFT textbook? - Physics Stack Exchange

Relativistic quantum field theory is wrong.

quantum field theory - Normal ordering of hamiltonian - Physics Stack Exchange

quantum mechanics - Is the wave-particle duality a real duality? - Physics Stack Exchange