Also, I always thought that the best card for ZEC mining is GTX 1070ti. My choice was the ASUS STRIX GeForce STRIX GTX 1070 Ti Advanced A8G 8.0 GB. The ratio of price and quality suits me.
Well, I do not know, the GTX 1070 ti is definitely the most energy efficient card, but I would probably prefer to take 2 GTX 1060 3gb, more hash rate, less costs, on daggerhashimoto can give 48 M/hash if you will be lacy to get Samsung memory, the only disadvantage is the power consumption and the fact that 2 PCE slots occupy.