Hmm, some interesting thoughts.
How about this question: How do you feel when you are in the zone ? What are the signs that tip you off that you have reached that place ?
The times that I have been in the zone (or at least I think I was in the zone), I have felt somewhat lightheaded, almost to the point of being in an "out-of-body" state. At that point I am care free and swinging freely, hitting the shots pretty much exactly as I would like. Now what makes me a little unsure of the authenticity of this zone state is that I think the light headedness may just be a result of loss of fluid. Sure I take in water, but given that I'm a heavy sweater I am guessing I have substantial net loss of fluid at this point. On the other hand it may just be that this is all likely to happen at the same time - i.e. that I reach my peak at the point when I am truly into the play, at which point I am also losing fluid, and that's what makes me light headed. Or perhaps the light headedness is just some symptom of having reached the elusive state.
So how do you feel when you are there ?