The improvements from AlphaGo -> AG Master -> AG Zero is by adding more generalization techniques and rely less on human intervention/data. AlphaGo Zero learns

The improvements from AlphaGo -> AG Master -> AG Zero is by adding more generalization techniques and rely less on human intervention/data. AlphaGo Zero learns only from self training. AGZ probably can be retrained to other board games, but the hardware cost to train is quite expensive. The estimated cost to train AGZ (for 40 days?) was $25M.