So for anyone not yet at the stage, the middle Z part LOOKS perfectly symmetrical and for most purposes, it is. However, the angled channel on the outside where the triangle-y looking pieces get bolted on absolutely matters.
I had it backwards and got the super long bolts through 3 of the 4 triangle-y things, and just couldn’t budge the other piece on. Parts were hitting, I even used a file to shave off some things thinking it was just a bigger than normal printed part.
Instructions don’t tell you this…be warned. Will save you LOTS of frustrated knuckles.