If you really have as much disinterest in all Mahayana thought as you say, and do not wish to discuss it, the sensible thing to do would be to refrain from making disparaging straw man arguments, comments and implications about it. I'm sure I've suggested this to you before.
Your criticisms of Nagarjuna, Madhyamaka, Sunyata and Non-duality are consistently off-target and unsupported by source material. Nagarjuna, for example, is abstract but very non-metaphysical. He has been compared in modern times to Wittgenstein, who was the leading figure in the Logical Positivist movement. That is about as non-metaphysical as you can get. Having said that, there are Mahayana concepts which really are very metaphysical or have been reinterpreted as such. Neither Emptiness nor Non-self mean non-existence, for example. Those misunderstandings are worth challenging I think. And that is what I try to do at least at times on ZFI. Just as your (and Bikkhu Bodhi's) misunderstanding of Non-duality as some sort of metaphysical theory about a Cosmic Absolute that is inconsistent with Buddhadhamma is worth challenging here.
There is, however no enforced orthodoxy of view on ZFI (Esangha had that and it wasn't pretty). Also, I'm not an active moderator there.
Also I'm not aware of having any 'pre existing Zen belief systems' . As I explained, Nonduality is an experience (of Nonself) not a belief. It is, however Zen terminology - but hey, Bikkhu Bodhi started it. I'm not a 'Zennist' or a 'Mahayanaist'. Zen just happens to be my main practice. I also sit with a Theravada group. Just last night I gave a talk there about Anatta. I'm just as comfortable with a Theravada theoretical framework - maybe even more so. One thing I greatly value about Theravada is the coherence of it's authoritative texts - especially the Nikayas - and in my experience so far, there may be less tendency towards misunderstanding. A coherent theoretical model is valuable.