a \begin{tikzpicture}[baseline]
    \draw[->] (-.5,-.5)-- (.5,.5);
    \draw[->] (-.1,.1) -- (-.5,.5);
    \draw (.1,-.1) -- (.5,-.5);
\end{tikzpicture}
- a^{-1}
\begin{tikzpicture}[baseline,xscale=-1]
    \draw[->] (-.5,-.5)-- (.5,.5);
    \draw[->] (-.1,.1) -- (-.5,.5);
    \draw (.1,-.1) -- (.5,-.5);
\end{tikzpicture}
= z
\begin{tikzpicture}[baseline]
    \draw[<-] (1.5,.5) .. controls (2,0) .. (1.5,-.5);
    \draw[<-] (2.5,.5) .. controls (2,0) .. (2.5,-.5);
\end{tikzpicture}