I have to correct myself. I just tried with Zenpage default and the current svn: The page chosen for homepage is selected as active in the page menu. Of course the problem is that only unpublished pages can be used as a homepage so it does not appear in the menu if not logged in anyway. (otherwise the menu would be confusing, wouldn't it?).
The home page is internally not the `index.php` but in this case `pages.php` as that is loaded instead.
You still have to put a a hardcoded link and check for the page directly like `$_zp_current_zenpage_page->titlelink == "<titlelink of the page>"`; Or you make a custom function out of it that also shows unpublished pages or this specific one.
I guess I also put a kind of `is_Homepage()` helper function on my list...