Playing Zone is an interesting topic to begin to explore, and at the beginning, it can seem that there is very little information out there about it, though like anything, there is more than one would think.
And the following few books are interesting reads into the topic of the Playing Zone.
In The Zone – Michael Murphy
Playing In The Zone – Andrew Cooper
Hitting The Zone – Steve Williams
The Rise Of Superman – Steven Kotler
Stealing Fire – Steven Kotler & Jamie Wheal
The Inner Game Of Tennis – Tim Gallwey
And it always helps to have a picture representation of it.
The playing zone, or getting into flow, can seem like a mysterious thing, though the more that one looks into it, that the Playing Zone has certain rules and parameters, that if followed, gets one into that hidden path