We could use diagonal arrows for the odd-numbered diagrams:

- `\searrow` produces an arrow pointing to south east \\(\searrow\\)
- `\swarrow` produces an arrow pointing to south west \\(\swarrow\\)
- `\nearrow` produces an arrow pointing to north east \\(\nearrow\\)
- `\nwarrow` produces an arrow pointing to north west \\(\nwarrow\\)

The commuting triangle example would look like this:

\[
\begin{matrix}
X & \xrightarrow{f} & Y \\\\
& \searrow & \downarrow \\\\
& & Z
\end{matrix}
\]

Unfortunately, I don't know of an easy and nice way of labelling the diagonal arrows; maybe we can draw some inspiration from [this Maths Stackexchange thread](https://math.meta.stackexchange.com/questions/2324/how-to-draw-a-commutative-diagram).