What's a Duotangle? Simply, it's a tile that's completed using only two tangle patterns. Here the two patterns are Fengle and Quandry. These are both official Zentangle patterns and instructions for them can be found following these links; Fengle and Quandry.
I used the basic square paper tile and then picked up my colored Pigma Micron pens. Some shading was added with the appropriately colored Prismacolor colored pencil.