Alright, so reading *********** confirmed what I was trying to translate from Mangareader's translation of the chapter.
Essentially, due to being composed of the souls of many shinigami, Zangetsu is a modified soul-turned-weapon that took the form of a hollow as opposed to an Asauchi. That being said, Shirosaki is Ichigo's real zanpakuto (aka his zanpakuto is a hollow). Ichigo's real power, however, lies in his Quincy lineage. Most people say that he was a shinigami that received hollow powers then Fullbring powers and finally Quincy powers, when in actuality he is a Quincy that borrowed shinigami powers and later manifested his hollow dwelling within his soul, with both deeds finally awakening Shirosaki. Juha Bach's blood running through Ichigo's veins (as it does with all Quincies) is what allowed him to enter Ichigo's psyche and masquerade as Zangetsu. Since both are genetically the same manifestation of Ichigo's power, Juha Bach and Shirosaki are in fact the same entity. Why this is the image of Juha Bach 1000 years ago, I'm not exactly sure. It could possibly be Aizen's doing. He could have tampered with White using souls of Quincies from long ago.
In summation, Hollow/Asauchi-infused Quincy + Former shinigami turned human via Gigai = Ichigo Kurosaki.