> 1. unzip an archive
> 2. re-zip the archive with a given compressor
> 3. compare each of the compressed chunks in the new archive with the same
> compressed chunk in the original archive. when a chunk in the new archive is
> smaller, replace that chunk in the original archive with the smaller chunk.

you just described how zipmax works. from the documentation, the equivalent to your point 3:

- ZipMax compares the sizes of each single file and creates a new one with a
mixture of the smalles files from the old and the new archives. If the new
one is smaller, it replaces the old one with it. If the new file isn't
smaller the old file won't be touched.


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