I wasn't able to determine from what I read yesterday if AlphaGo Zero played vs AlphaGo or vs itself (AlphaGo Zero). This probably isn't the place to ask, but if it is, do you know?
It was trained with self-play and evaluated on AlphaGo Lee (the version that beat Lee Sedol) and AlphaGo Master (the version that beat Ke Jie and I believe a number of online matches against top-ranked professional players).