As it turns out, ZFeeder uses a ton of globals via includes, and doesn't encapsulate very well at all. I'll give you an example:
A function contained in a file included by the main zfeeder.php, parseOpmlFile(), accepts an OPML filename parameter and returns a string value as a success result. In that function, it sets a global variable that is accessed by the main file. (This is kind of sloppy, IMO.)
Because EzStatic includes the main ZFeeder file inside a function, the globals in the second-tier include aren't in the same scope as the main zfeeder.php file, therefore they can't be accessed correctly.
This is a bug that should be reported to the ZFeeder folks, since they seem to be under the impression you can just drop their include statement anywhere and get working feeds. They should probably instead either return those global results by reference (that's kinda taboo in PHP, but doable), or return 'false' on error and the actual results on success, which is what most people seem to do.
You might consider a different reader. Ever try FoF? That seems to work via EzStatic.