Thank you Mirek. Nowadays, do you advice to use zstd better than 7z?
Thats apples / oranges...
zstd is not about improving compression levels, but about doing high speed compression with zlib levels.
7z (LZMA) has better compression, but zstd is much faster.
On the opposite side of spectrum is LZ4 (by the same author), which is significantly faster than zstd (about twice), but the compression is not that great.