[eclipse] how to 'export' an external arcive ?

hi all,

I'm tryng to rebuild an old project from scratch. this project needs
com.oroinc.test.regex.* classes. the needed .class are located in .zip
file containing the folder tree com|oroinc|text|regex|*.class

I tried to add the classes with "import > archive file". the compiler
does not report errors on the import statement but reports error as
soon as I try to use whatever come from these .class

so I deleted what I've just imported and added the .zip archive to my
project with "Build Path > Add external archives" but when I export the
resulting project, the external archive (and so, the corresponding
..class) is not included in the resulting .jar file :(

where am I wrong ?