An equation with Feyman diagrams inside

Question

I want to include this equation number 6.87 and 6.88 as same as in the screenshot to my project, please give some help to do this...

Answer 1

Disclaimer: I'm an absolutely sporadic user of TikZ and I have no experience whatsoever in drawing Feynman diagrams with it (I still use feynmp for that...) but here's a shot at it

\documentclass{article}
\usepackage{tikz}
% \tikz picture vertically centered on math axis
\newcommand{\ctikz}[2][]{\hbox{\mathsurround=3pt$\vcenter{\hbox{\tikz[#1]{#2}}}$}}
\usetikzlibrary{arrows.meta}
\newcommand{\I}{\mathrm{i}}
\begin{document}
[
Z[j] =
\frac{\displaystyle \biggl[ 1 - \frac{\I,g}{4!} \int 
      \biggl(
      -3 \ctikz{ \draw(0,0)circle(0.2); \draw(0.4,0)circle(0.2); }
      + 6\I
        \ctikz{
          \draw{Rays[]}-{Rays[]}--(0.8,0);
          \draw(0.4,0.2)circle(0.2);}
      + \ctikz{
          \draw{Rays[]}-{Rays[]}--(-0.3,-0.3);
          \draw{Rays[]}-{Rays[]}--(0.3,-0.3);}
      \biggr)
      \exp\biggl(-\frac{\I}{2} \int J \Delta_{\mathrm{F}} J \biggr)\biggr] \mathrm{d}z}% end of numerator
     {\displaystyle 1 - \frac{\I,g}{4!} \int \Bigl(-3 \ctikz{\draw(0,0)circle(0.2);\draw(0.4,0)circle(0.2);}\Bigr) \mathrm{d}z}
]
\end{document}