The z curly cable has some wires cross that is required for the z axis to move. (in fact, the x and y’s have inner tube wires that also have crossed wiring that are required for their respected axis to move properly). Removing this z curly cable will result in the z motor not moving properly. The extension cables are not meant to be replacement cables, but rather extend the current wires. Some people that are using 3rd party drag chains are either 1) straightening out the curly cable or 2) making their own sets of cables and crossing the wires themselves.