It is easy to escape characters that are special to zsh itself.
It is not so easy to escape characters that are special to POSIX
extended regex. (The rules are hardly impossible to work out,
but they're not straightforward either.)
I think that's the crux of it. I do understand what you're saying.
If there were a fix via some form of quoting or whatever, I'd use
it, so I thought I'd ask, but as you say, there are more robust
solutions. I'm fishing for something easy but in practice this is
hardly an issue, I'm just interested in the principle of the thing.
I've come to learn that zsh can do almost anything if you get the
invocation just right.