Madara did a lot while on the verge of death.....
Madara admitted that he awakened Rinnegan while on the verge of death (mangastream translation) and apparently accomplished a lot before ever attaching himself to the Gedo Mazo.
1. He summoned Gedo and used it to begin cultivating Zetsu clones. From what I can gather, this means that he only had a small amount of Senju DNA at that time, and essentially created the giant lotus flower by utilizing the Gedo Mazo itself, this obviously took a substantial amount of time, perhaps months or years:
2. Apparently, before ever having access to the lotus flower and Zetsu clones, Madara journeyed to the Rain village, killed a fodder uchiha along the way, stole only one of his eyes for some reason, and transplanted both of his Rinnegan to Nagato. Then directly afterward, he journeyed back with only that one sharingan he stole, all while on the verge of death.
Obviously Zetsu was not around to help him at this time. Having just awakened the Rinnegan and gotten access to the Mazou, Madara did not have zetsu clones to help him. As more proof, Zetsu admits that Madara was the one that did the transplant:
If you read the mangastream translation, Zetsu goes as far to say, "Apparently Madara transplanted them without Nagato realizing", meaning he was only told about the events from Madara, further proving that Madara did this before he had Zetsu to help him.
Basically what I'm getting at is that its implied that Madara likely had to attach himself to the Mazou as soon as he summoned it in order to survive. But the manga also implies that Madara made this long journey alone as a 75+ year old man (on the verge of death) managed to kill a fodder Uchiha along the way (assuming he had no stored sharingan at the time) and made his way back to his base without any means of quick transportation. By this I mean that with Rinnegan he can fly, but after giving them to Nagato, he had no fast way to travel back to his base.
Anyone else find this hard to believe?