Simple works best. When your instructor tries to make something simple into something complicated, secret, or mystical, find another instructor. This is not rocket science.
Ki, chi, internal force, in the zone, etc
These are basically all mumbo jumbo. All they really involve is concentrating your mind and body on the task at hand with such intensity that everything else becomes secondary. Many athletes of other sports speak of this feeling, they just do not make it into something mystical and complicated. Any athlete that is a the top of his or her game experiences it.
Breathe deep, slow breaths through the nose using the diaphragm and exhale slowly through the mouth using the diaphragm. That is about it for breathing. Everything else is mumbo jumbo.