Board Thread:Theories and Speculation/@comment-34661853-20181111160651/@comment-734582-20181111161449

>The difference in difficulty lies in the fact that the rinnegan requires the EIEN NO MANGEKYOU SHARINGAN of a reincarnation of INDRA along with the cells (chakra) of an ASHURA reincarnation

No it doesn't. All that's needed is the chakra of an Indra to mix with an Ashura, as per Black Zetsu's explanation.