Do we really want to go there?
I mean, we could… on the other hand, there is z80 Heaven, which is already going fairly strong (it's been mostly inactive the past couple of months, but that situation will hopefully change), while we are supposedly "TI-Basic" Developer.
There's also the issue of who'd be writing it. I know several of our members know z80 assembly. Most of them are either editing z80 Heaven already, or have been inactive for some time. You know assembly, and from looking at the code you've posted I think you have good chances of, say, writing a working assembly program that does something cool… I don't think you've seen enough of the big picture to be leading the writing of a tutorial, though I'm sure you could fill in details of an already-formed one. I know I don't want to do it, I only today got myself to start working on the 68k section again, and I'm not going to be splitting my attention between that and anything else in the near future.
In short, I don't see that there's sufficient need for a z80 section to this site, or sufficient interest for it to be effectively written.