Why not just store the XML in an XMLTYPE column in the DB. As you are on 22.214.171.124, you will be using the default storage format of SECUREFILE BINARY XML and that provides a compressed form of the XML that is easier for future parsing efforts. I can't speak how it would compare to a .zip version of the XML.
Without knowing more why you think LOBs need to be involved, I would avoid them completely since they are not setup for efficient XML storage/usage and the XMLType datatype is.
As for the .zip abilities, some good reference point (that started from)
[url http://odieweblog.wordpress.com/2012/01/28/xml-db-events-reading-an-open-office-xml-document-xlsx/]XML DB Events : Reading an Open Office XML document (.xlsx)
and eventually leads you to
[url http://technology.amis.nl/2010/03/13/utl_compress-gzip-and-zlib/]Utl_compress, gzip and zlib
[url http://technology.amis.nl/2010/06/09/parsing-a-microsoft-word-docx-and-unzip-zipfiles-with-plsql/]Parsing a Microsoft Word docx, and unzip zipfiles, with PL/SQL