travis said:
[...snip, snip ....]

>   Which (I thought) was exactly what xml was supposed to be
>   used for.  (not complaining about the use of zml, only
>   pointing out that other options already exist.'

except those "other options" do _not_ "already exist", not in
a form project gutenberg can use to facilitate its workflow...

and if you think you can develop such a thing, then please do,
because project gutenberg has been seeking you for a decade.
nobody else has been able to create such a solution for them.