Worse, I seem to need help posting a message on this forum 
. I accidentally submitted in mid-sentence, tried to withdraw it so I could finish writing before publishing, ended up I guess soft-deleting it, but was unable to figure out how to revive it and resume composing. It’s downright embarassing.
As for zend-navigation, short answer: no, maybe I don’t need help at the moment.
Long answer: I was going to ask about how to get breadcrumbs to render a 4-level thing as described in the subject line, but I think I may have figured it out, at least theoretically – in my mind, while walking the dog. (Haven’t we all had that experience of solving a technical problem by standing up, walking away and doing something else for a while?) This of course was after RTFM to no avail.
But I also think I need to step back and re-think the whole approach to my routing and navigation. It’s a rather large project with a lot of different entities to manage, more than one way to get to the same place, so it’s taking extra cognitive effort to devise a sane navigation.
I’ll be back when I get stuck for real 
, thanks.