Curious if you compared Zstd against Brotli. I'd expect Zstd to beat Brotli by a fair margin for non-text payloads (+ faster for decompression which matters since these are compressed once / decompress many).
We didn't, and I'll have to make a note to investigate zstd for my own purposes later! Brotli is kind of the only game in town since it's shipped in every web browser now as a transport codec (the other one is gzip)