We havent seen madara's powers yet. But jinckurickis that have one rennigan and presuable one ems are no pushovers. Bascially 6 jinchukicki with an ems and a rennigan + a powerful ninja with an ems + rennigan.
This fight is very tricky because all the ninja's cannot die. All the jinckuricki are dead, nagato and itachi are dead and madara so far seems immortal.
I think for nagato and itachi to win, nagato has to do the majority of the work. Also i assume you mean a fully able bodied nagato. Anyway if nagato can remove the souls of the former jinckurciki and itachi seals a few aswell with the totsuka sword, then they stand a chance.
This is way too far fetched, ill go with madara + former jinchurickis