From 0.5 to about a "1." It takes a lot of work/practice to become proficient. Zimmerman was diligent, coachable, just didn't have the athleticism, childhood athletics.
O'Mara asks about boxing. First, get comfortable with your own body, how to control their body. Footwork, calisthenics. Also a 0.5 on the 1-10 boxing scale. He was a hard worker, but it takes a certain amount of time to develop. People with good athleticism are ring ready in 1-2 years. Zimmerman never got in the ring. He wasn't skilled enough. Zimmerman never got past shadow boxing and heavy bag, he did not know how to punch. Absolutely not at a point where he could box somebody else.
He progressed little beyond 0.5 on boxing. Physically better as to body weight, but lacked athleticism. Grossly obese.
Did he ever get to kick boxing? No. First has to be able to box. Zimmerman did not have a handle on punching.