here is the solution
packcmd = zcmx64 a -s -r -m8
$$arcpackedfile$$.tmp $$arcdatafile$$.tmp
================================================== =======
Compressed 20 files, 75,397,181 => 17,850,409 bytes. Ratio 23.6%
Compression time: cpu 0.06 secs, real 32.83 secs. Speed 2,297 kB/s
All OK