man zshbuiltins excerpt:
The third form of cd extracts an entry from the directory stack, and
changes to that directory. An argument of the form `+n' identifies a
stack entry by counting from the left of the list shown by the dirs com‐
mand, starting with zero. An argument of the form `-n' counts from the
right. If the PUSHD_MINUS option is set, the meanings of `+' and `-' in
this context are swapped. If the POSIX_CD option is set, this form of
cd is not recognised and will be interpreted as the first form.
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