I still don't think Browne's elbows were illegal except for 1. After seeing a larger gif it is obvious that Browne actually changed his elbow strikes for the last 2 strikes and that they approached more from the side and landed close to Gonzaga's right ear(can't see it from above but the side shot shows this). First 2 shots pretty much hit Gonzaga right on his left ear as well.
The 4th strike was definitely illegal but that was because Gonzaga slumped unconsciously into it. The 3rd strike that caused the knockout was close and I can't find a large enough gif to be sure but from what I have seen I think it was just legal as it landed further up the head away from the neck area.
Browne was actually trying quite hard to keep the elbows legal, his only other option would have been to not throw them. I actually am glad they allow strikes like this for the most part since guys defending takedowns already have so few options for strikes.