Just tested my 84M fake social media file - `jcof` gives 44M, `gzip` gives 19M, `jcof+gzip` gives 17M. In essence, you've gained 2M for two CPU intensive procedures instead of one. Doesn't seem all that worth it?
Prompted me to check if the higher zstd levels worked any better on my 84MB fake social graph - nope - and then if LZMA was any good - yes, `lzma` at 5 or higher on the raw JSON beats `jcof | lzma` by ~2M every time. `lzma -4` beats it by ~400k.
If I sort my object keys (a la `jq -S`), `lzma` beats `jcof|lzma` at every level (`gzip` never gets close, `zstd` gets closer.)