I found the article about Papelbon more interesting that the article about Zambrano. I came away from the article about Zambrano with a feeling that the author was really fishing for something. I didn't really see a signficant difference between the before and after pictures.
Now, I think there was a more noticeable difference between the before and after pictures of Papelbon. In fact, I noticed a few things myself. Specifically, while it's hard to tell given the camera angle from the rear, it appears from his posture that his head and shoulders are stacked upright more in the earlier clips whereas they get out front sooner/further in the newer clips. I noticed that he tucks and sweeps his glove sooner in the newer clips. He also drops his glove in the newer clips. I also noticed that his back foot appears to lift off the ground a frame sooner in the at least one of the newer clips. These things are indicators that he is opening up sooner - as was discussed in the article. I would agree that Papelbon's issue is mechanical (though I can't really rule out a medical issue). Maybe the pitching coach tinkered too much. After all, the article did mention the coach trying to get him to "get the feeling of his left elbow actually brushing past his left rib cage" and "keeping it tight".