OK, I'm a novice but I think this one would even cause many to scratch their heads. The picture won't tell the whole story clearly but hopefully I can paint the picture to fill in the gaps.
This is a transition from one rectangle to another with no 90 degree corners, all faces are angled. There is a flange on both ends that isn't shown in this image. While it appears this is a legitimate sheetmetal transition, it's not. I started with a solid extrusion and used cut extrudes to get the profiles needed. I then tried shelling, ripping and insert bends to no avail.
I removed the bends and rips and then essentially "clad" the surfaces with base and edge flanges from sketches normal to each face. This is what you are seeing in the picture. Unfortunately, each cladded part now needs to be it's own part and put back together in an assembly but because the sketches were traced, I can't figure out how to break the link so when I suppress the original block extrusion I'm left with the sheetmetal parts.