I heard on tv that the refs are told to be so harsh on players elbowing for those fouls directly aim the players' heads and therefore might be so dangerous. He elbowed both Zambrotta and Chiellini and he should have been punished with two yellows for each. Of course, if the ref had given him a yellow earlier for the foul he committed on Zambrotta, he most probably wouldn't have elbowed Chiellini later