A ZIA is often representational while traditional Zentangle art is almost always non-representational. It was sometimes said that if it had color then it was a ZIA, but in recent years color has become another layer to the complexity that the Zentangle method has to offer.
I feel the Zentangle Method has grown organically as this very simple method continues to bring forth art that is far deeper and more sophisticated than we ever anticipated. And really it is because of all the amazing enthusiastic Zentangle artists all over the world challenging and creating. I am so humbled and thrilled with how awesome it is. The slow addition of color has been delicate and appropriate to what the method stands for. So I realize this doesn’t really answer the question.
A basic original Zentangle is a done on a 3.5″ square piece of white paper with black ink and shades of gray. It is non-representational. It is created using the Zentangle Method