I have also tested bzip3 and initially I encountered a great number of cases where bzip3 was much better than zstd from all points of view, i.e. compression ratio and execution times, for any zstd options.

Unfortunately, later I have also found other cases where the bzip3 performance was not so good.

I spend a lot of time on compression/decompression, but sadly there is no algorithm that can be said to be superior to all others in all circumstances, so for optimum results you must still be prepared to use any of them.

Even the ancient gzip is preferable in certain cases, when speed is more important than compression ratio, because sometimes it happens to provide a better compromise than newer algorithms.