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It depends on what is meant with the term "Support ZIP archives" - what should XOOPS support here? "Upload a ZIP archive to publish on the web" means what, exactly?
Regarding workflow, the XOOPS module structure leaves a lot of autonomy to the modules, giving flexibility in exchange for looser structured content. Therefore it is up to the individual modules to grant the user a workflow (I suspect you mean something along the lines of someone submitting content, another one publishing it) - which is a rather established feature in most modules, but not centralised as in several other systems. It's the same with a "trash bin" - since content is not centralised, it is also not easy to have a centralised "trash bin" to gather deleted content for re-evaluation or purge.
XHTML compliance again depends on the modules. It is definitely possible to create XHTML valid sites with XOOPS, but individual modules can break this compliance if they are not coded properly.
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Cusix Software