Available in GDAL and MapServer master!

[rouault]

The implementation has just been merged into GDAL and MapServer master repositories.

You can for example test QGIS+GDAL with Conda packages:
conda create --name sozip_test
conda activate sozip_test
conda install -c gdal-master gdal
conda install -c conda-forge qgis

And for example with a large GeoPackage file (filenames to adapt of course):
sozip -j output.gpkg.zip /path/to/input.gpkg
qgis output.gpkg.zip