How to determine the Z_Axis edge of irregular multifax surfaces

[syalways]

There is a question I would like to ask, like this kind of irregular multiple surfaces how to determine which is the z-axis edge, I tried several directions, but the resulting path is not right.can you help answer it, thank you very much.

[xuanxuanbingo]

Hello, I want to ask have you successfully reappear the whole process on the grasshopper?