RE: how to install z3ta+ vst
You need the subfolder structure to come along with the .dll. Perhaps it's been changed, but that used to be contained in \...rgcaudio z3ta+\rgcaudio z3ta+. Under that level, you'll find subfolders for Arpeggio, MIDI, Presets, Skin, Tunings, User Manual, and Wavetables.
z3ta+ needs access to those folders to function properly. In the external VST Adapters, you could just point to an additional location. With S6, I'd guess that you'd be better off extracting the .zip file contents directly to the VSTPlugins folder. Either way, you need the rest of the files along with the .dll.