The diagram clearly shows having been drawn with Xy-pic (the horrible arrow tips are revealing).
Here's how you can do it with tikz-cd
\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
\[
\begin{tikzcd}[row sep=1em,column sep=1em]
& & 0 \arrow[dr] & & 0 & & 0 \arrow[dr] & & 0 & & 0 \arrow[dr] & & 0\\
& & & C_2 \arrow[ur] \arrow[dr] & & & & C_4 \arrow[ur] \arrow[dr] & & & & C_6 \arrow[ur] \arrow[dr] \\
& & A_1 \arrow[rr] \arrow[ur] & & A_2 \arrow[rr] \arrow[dr] & & A_3 \arrow[rr] \arrow[ur]
& & A_4 \arrow[rr] \arrow[dr] & & A_5 \arrow[rr] \arrow[ur] & & A_6 \arrow[dr] \\
& C_1 \arrow[ur] & & & & C_3 \arrow[dr] \arrow[ur] & & & &
C_5 \arrow[dr] \arrow[ur] & & & & C_7 \arrow[dr] \\
0 \arrow[ur] & & & & 0 \arrow[ur] & & 0 & & 0 \arrow[ur] & & 0 & & & & 0
\end{tikzcd}
\]
\end{document}
![enter image description here](https://i.stack.imgur.com/IMoHL.png)
Here is the version with only five terms in the long exact sequence. The idea is that in the long sequence in the middle we jump over one column, which makes room for the terms of the diagonal short exact sequences.
It's just a patience game of counting steps. You think of this as a matrix, with &
for separating cells in a row and \\
for ending a row; trailing &
can be omitted. With \arrow
you specify the target cell.
\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
\[
\begin{tikzcd}[row sep=1em,column sep=1em]
& & 0 \arrow[dr] & & 0 & & 0 \arrow[dr] & & 0 & & & & 0\\
& & & C_2 \arrow[ur] \arrow[dr] & & & & C_4 \arrow[ur] \arrow[dr] & & & & C_6 \arrow[ur] \\
& & A_1 \arrow[rr] \arrow[ur] & & A_2 \arrow[rr] \arrow[dr] & & A_3 \arrow[rr] \arrow[ur]
& & A_4 \arrow[rr] \arrow[dr] & & A_5 \arrow[ur] \\
& C_1 \arrow[ur] & & & & C_3 \arrow[dr] \arrow[ur] & & & &
C_5 \arrow[dr] \arrow[ur] \\
0 \arrow[ur] & & & & 0 \arrow[ur] & & 0 & & 0 \arrow[ur] & & 0
\end{tikzcd}
\]
\end{document}
![enter image description here](https://i.stack.imgur.com/JH7nc.png)
Here's the doubled diagram, although I can't understand its meaning.
\documentclass{article}
\usepackage{tikz-cd}
\begin{document}
\[
\begin{tikzcd}[row sep=1em,column sep=1em]
& & 0 \arrow[dr] & & 0 & & 0 \arrow[dr] & & 0 & & 0 \arrow[dr] & & 0\\
& & & C_2 \arrow[ur] \arrow[dr] & & & & C_4 \arrow[ur] \arrow[dr] & & & & C_6 \arrow[ur] \arrow[dr] \\
0 \arrow[dr] & & A_1 \arrow[rr] \arrow[ur] & & A_2 \arrow[rr] \arrow[dr] & & A_3 \arrow[rr] \arrow[ur]
& & A_4 \arrow[rr] \arrow[dr] & & A_5 \arrow[rr] \arrow[ur] & & A_6 \arrow[dr] \\
& C_1 \arrow[ur] \arrow[dr] & & & & C_3 \arrow[dr] \arrow[ur] & & & &
C_5 \arrow[dr] \arrow[ur] & & & & C_7 \arrow[dr] \\
0 \arrow[ur] & & 0 \arrow[dr] & & 0 \arrow[ur] & & 0 \arrow[dr] & & 0 \arrow[ur] & & 0 \arrow[dr] & & 0 \arrow[ur] & & 0 \\
& & & C_2 \arrow[ur] \arrow[dr] & & & & C_4 \arrow[ur] \arrow[dr] & & & & C_6 \arrow[ur] \arrow[dr] \\
& & A_1 \arrow[rr] \arrow[ur] & & A_2 \arrow[rr] \arrow[dr] & & A_3 \arrow[rr] \arrow[ur]
& & A_4 \arrow[rr] \arrow[dr] & & A_5 \arrow[rr] \arrow[ur] & & A_6 \arrow[dr] \\
& C_1 \arrow[ur] & & & & C_3 \arrow[dr] \arrow[ur] & & & &
C_5 \arrow[dr] \arrow[ur] & & & & C_7 \arrow[dr] \\
0 \arrow[ur] & & & & 0 \arrow[ur] & & 0 & & 0 \arrow[ur] & & 0 & & & & 0 \\
\end{tikzcd}
\]
\end{document}
![enter image description here](https://i.stack.imgur.com/08HUW.png)
Best Answer
Here are solutions with
xy
andtikz-cd
. The idea is the same, think on them as matrices.