# How to draw two arrows above each other?

Here is the figure I want to draw:

My big problem is the two arrows above each other with something written above and below. I tried the following:

\documentclass{book}
\begin{document}
$\begin{tikzcd} & \bullet & \bullet \\ \bullet & \bullet & \bullet \arrow[from=2-1, to=2-2] \arrow[from=2-2, to=2-3] \arrow[from=1-2, to=1-3] \end{tikzcd}$
\end{document}


But it did not quite produce what I want.

Use the functionalities of tikz-cd:
    \documentclass{book}
$\begin{tikzcd} E \rar & \prod\limits_\alpha D_\alpha \arrow[r, shift left=0.75ex, "c"] \arrow[r, shift right=0.75ex, "d", swap] & \prod\limits_f D_{c(f)} \end{tikzcd}$