You can also make ZIP files smaller by switching the compression from Deflate to Zstandard. In the one case I tried this, this resulted in a 60% file size decrease [1]. Unfortunately Info-ZIP which provides the unzip command hasn't had a release in 18 years, so it doesn't support this newer compression/decompression method. You have to use 7-Zip instead.
[1] https://github.com/UKGovernmentBEIS/inspect_ai/pull/3145