Hi,
If your goal is to access the SFX archive and extract from it, you don’t have to do anything. Just feed your “SFX zip volume stream” to ZipArchive just like you would any standard zip file.
A SFX archive is, actually a normal zip file that has a executable part prefixed to it at the beginning of the file. But the zip file format places all relevant zip information at the end of the file. So ZipArchive will be able to handle a SFX archive without issue.
Does that fit your usage scenario?