Lets me make this topic more intellectual. (and please no name calling. Yazen dont be offended with tones, we all talk that way sometimes, none of the reply tried to look down on you. But your post does seems a bit useless to some of us, its to be expect always, same as all threads.
But lets say we treat it seriously.
In story telling, there is blur line between real entities and personification of ideas and other objects. Assuming Ichigo is a real person, we probably never get to see anything else but just him fighting with a sword. But in the word of bleach the whole story is based on the existence of shinigami and souls. Within Ichigo alone, the sword has a spirit of its own, and then it was said that white Ichigo is just Zangetsu transformed and crossing to the darker and more powerful side. yet for Ichigo to be stronger, he has to reign over him, in order to appear sane and...stuff. Look, a lot of this are just devices created by the author to focus on how Ichigo power up and to make the manga interesting.
That is the nature of imagination. KT cant just write a story with just a guy's dream up this world, in reality he is just a student. Thus KT makes believe of all this that way.
But KT, besides being a cheapskate with his art, he is a poet and an intellectual. Everytime Ichigo transform, iit s where KT tell you how you should really look at his manga, but i think a lot of ppl dont give it much though. I wont quote anything, but to me Ichigo simply has a fighting spirit, it gets tronger and "transform" to protect ppl he cares about. In other words, being a shinigami, being a hollow, all of that is just Ichigo's fighting spirit. I think its the same for everyone else. The "moral" of this is that we all have a soul, whatever form it exists, it is a part of that individual, not a separate existence. In the case of Shinigami and Hollows, its just a personification of good and evil souls and the strength associating with them. In the case of vizards and ichigo, it's really KT trying to say: there is no clear line btween good and evil, sometimes you cross them. As you can see, there are even good hollow, Nel for example, so she crossed back and forth, as we all do in real life.
In short, Zangetsu, WIchigo, and the fullblown Hollow Ichigo are just stages of the same Ichigo's fighting spirit. It is simple as that. He is the main character, so there is more stretches on the idea compared to everyone else. I know some readers are very young, and maybe just forget how to look beyond the text of a story. Here is a reminder. Thank you for reading.