Co-equalizer diagram in tikz-cd in LaTex

Question

Can someone help me to draw a horizontal parallel arrows as a co-equalizer diagram in tikz-cd?

An example of co-equalizer diagram is:

Thanks in advance!

Answer 1

You can go with tikz-cd:

\documentclass{article}
\usepackage{tikz-cd}

\begin{document}
\[
\begin{tikzcd}
X \ar[r,shift left=.75ex,"f"]
  \ar[r,shift right=.75ex,swap,"g"]
&
Y \ar[r,"q"] \ar[dr,swap,"q'"]
&
Q \ar[d,densely dotted]
\\
& & Q'
\end{tikzcd}
\]
\end{document}

Answer 2

Just for fun, a pstricks solution:

\documentclass[pdf]{article}
\usepackage{pst-node}

\begin{document}

\[ \psset{arrows=->, arrowinset=0.25, linewidth=0.6pt, dash=3pt 2pt, nodesep=3pt, labelsep=2pt, colsep=1.2cm, rowsep=1cm}
\begin{psmatrix}
  X & Y & Q \\%
   & &Q\smash{'}
%%%
 \ncline[offset = 0.6ex]{1,1}{1,2}\naput{f} \ncline[offset = -0.6ex]{1,1}{1,2}\nbput{g}
 \ncline{1,2}{1,3}\nbput{q} \ncline{1,2}{2,3}\nbput{q'}
 \ncline[linestyle=dashed]{1,3}{2,3}\nbput[npos=0.45]{u}
\end{psmatrix}
\]

\end{document}