Such symmetrical angular geometric shapes are very unusual for nebulae. This nebula is probably generated by a binary star system, and both stars have ejected cones of matter in opposite directions. These cones have right angles at the base, and they are turned sideways to the observer. In support of the cone hypothesis, you can specify radial spokes that run from the center of the image. They probably run along the walls of the cones. They would also have merged into a ring if the nebula had turned its other plane toward us.