https://unix.stackexchange.com/questions/59537/display-the-function-body-in-bash

declare -f <cmd>

which only works in zsh, delcare -f works in both zsh and bash.

Remove the broken line. What is the broken? With your feeling...!

cp "$HISTFILE" "$(mktemp --directory zsh-history-backup.XXXX)"
hx "$HISTFILE" "+$(<"$HISTFILE" wc --lines)"