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As I have described in https://www.dropboxforum.com/t5/Dropbox-files-folders/Downloaded-zip-file-content-is-not-compressed-storage-method/m-p/536933, currently if you download a folder from Dropbox, the generated zip content is not compressed.
It would be nice if the zip content was actually compressed - in fact I was surprised by the fact that it was not, as compression is something one would expect for granted from a file storage service as popular as Dropbox.
While compression may incur some extra processing on Dropbox's end, I'm guessing there's major benefits to be gained in terms of server/client bandwidth usage, download duration, etc. In my case the folder contained a few PDF files, and could still have benefited from a ~15% size reduction (if deflate compression were used); the actual reduction could be massive for textual content etc.
To reduce unnecessary processing/overhead, Dropbox could skip trying to compress file types that are known to be already compressed or uncompressible (e.g. videos, zip files) - or expose an option for the user to decide/request compression at the folder download action itself.
