I have dabbled in zentangle. The original zentangle is doodling with pen and paper and then shading with pencil. But it lends itself to quilting. I have never heard of zentangle piecing. Here is a picture of some zentanglesque quilting I have done (the background behind the cat). While not zentangle in the true sense (which is most often associated with repetitive designs and doodle designs broken down into very basic elements) it does have a sense of zentangle.
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