These Z-Aim scopes are a piece of chinese junk, the 2-20 and 3-30 (and a 1-6) were handed over by the swedish importer to a guy on a swedish forum. The result of the review/testing was not flattering, in fact devastating.
The 1-6 was way better, the reviewer even planned buying one.
I have come across the VisionKing scopes and other brands from China imported directly to Sweden or via a detour to US or Germany (re-naming) and I´m surprised that it´s possible to sell them at all.
I have an old Weaver V9 that´s constantly used by friends in need while their chinese scopes are going through the "road of warranty" due to optics problems, reticle issues and mechanical defects.