COMPRESS-390, there are requirements of the zip content to be mapped directly into memory and therefore may require special alignment on the embedded files. E.g. libraries may be aligned to page (4096-bytes) boundary, images on 4-bytes boundary etc. By alignment it's meant the offset from the beginning of file where the actual data stream starts, not the header.
One of the cases was (still is?) Android APK for which zipalign utility was created.
It would be useful if commons-compress ZipArchiveOutputStream supports something similar directly in its API.