it them?④The very richness and complexity[of③ the meaningful

it them?
④The very richness and complexity[of③ the meaningful relationships (②that kept presenting and rearranging themselves/on all levels,①from abstract intelligence to profound dreamy feelings/)],made it/difficult for Proust to set them out coherently/.
请问.最后一点出现的it和them是不是同时都指代relationship
还是
it作为类似于形式主语的作用吗?