Yeah, I'm far from an expert on anything about this either, but even in my limited understanding I can see the distance between Zen and other Mahayana practices. My flow chart's fuzzy, I don't know enough to know what carries through from where and why. Simplest answer that makes the most sense to me so far is that Theravada asks, "How do I escape samsara?" while Mahayana asks, "How do we escape samsara?"

Your reasoning, tools, and personal experience aren't on blast, I'm down with whatever works for you, too. I just learn out-loud in a kind of abrasive way. Everything is to illuminate some aspects of Buddhism for the sake of the discussion.

Like how it's hard for me to reconcile, for instance, the first line of the Heart Sutra (which by your admission was Dogen Zenji's jam) making appeals to Avalokiteśvara-The-Friendly-Ghost when the entire point of Buddhism is insight into the nature of reality. Huh?

Schools of Buddhism are hugely varied, and nuanced, and sort of tricky to dislodge a western Judeo-Christian bias when examining it since there is no sense of all-or-nothing acceptance or damnation. It's all whatever works for whoever. Except maybe in Pure Land, but that's just accepting grace or something.

Speaking of Judeo-Islam-Christian bias, I've never been able to understand the narcissism and myopia on display by practitioners of those religions that humans forever all over the world and for all time have had their own belief structures and yet theirs is in some way special.