All things are possible through math, my son 
If I’m understanding what you’re trying to do, you need to rotate the offsets from the old part using the rotation of the part they belong to. It looks like you’re rotating the new part, but not the offset from the old part. You can use the ‘Rotate Vector’ node with the rotator input being the rotation of the old part, and if you only want two dimensions, just leave the Z of the input vector set to 0. If the origin (pivot point) of your parts is not in the center of the mesh, it will complicate things, but the idea is still the same.