I had a similar sounding issue with my ZT 770. The pins (not screws) in the handles were so damn tight that I could actually not keep screws in the knife and have no risk of it coming apart. What I did was get a pair of plastic handled scissors and use the handle on the gap in the handle to slowly pry it apart. I damn near had to hammer it back together. Sometimes the tolerances are wonky, not sure if the knife being that tight is good or bad.
If you really want to patina the blade you should find some hard plastic and slowly pry the knife apart. I would suggest knowing what you are doing before you try, though. I lost one knife because the damned thing just plainly would not go back together (not even a hammer helped).