^you're right KaktoR,
I was using most recent version of libzstd without any success but using 1.1.4 from 2017 worked like a charm! If I may ask, how can one pinpoint exact version of libzstd to use? I tried everything, yes I even tried different versions of libzstd but it never occurred to me that I should be using 7 years old dll version
Thanks again,
best regards