[Zope] Converting HTML to StructuredText (and the reverse)

I'm interested in converting HTML to StructuredText (and back again). The "back again" part is pretty easy, although I don't want headers to be <H1>, I want them to be <p class="h1">. If you can give me any hints about that I'll be grateful. Is it possible without subclassing the current classes? Anyway: The big issue is converting from HTML to StructuredText. I can't find any classes that does this today, if anybody have any code for doing this or can point me to some I'd be very happy. Thanks!