This is only partially fixed after the big “mirrors” update.
Zooming into a mirror still takes you to the “original” instance’s document, which is an incorrect behavior for a true mirror that is agnostic of which item is the “original”.
However, at least the “back” button does take you back to the document you actually started from, so there’s a lot less potential for getting disoriented.
Of course, it “shouldn’t matter” in terms of editing the items in the resulting zoomed Pane, but if a user chooses to jump up the Outline using breadcrumbs after making their changes, they’ll unexpectedly end up in a totally wrong document.
I’m bumping the priority of this because it “should” have already been addressed, plus it’s been around for a while.