I have 2 rigs on ZEC mining :

RIG01
7x MSI 1060 Gaming X (320-340 Sol/s)
4x ZOTAC 1070 amp (464-492 Sol/s)
1x GIGABYTE 1070 (465-487 Sol/s)
=>1070 cards on power limit %100 and Memory clock (+800-900 in afterburner)
=>1060 cards on power limit %100 and Memory clock 4475 (+675 in afterburner)
Total speed : 4777 Sol/s (MAX)

7x MSI 1060 Gaming X (320-340 Sol/s)
4x ZOTAC 1070 amp (420-440 Sol/s)
1x GIGABYTE 1070 (410-420)
=> 1070 cards on power limit %60 and Memory clock 4151 MHz (+300-350 in afterburner)
=> 1060 cards on power limit %100 and Memory clock 4475 (+675 in afterburner)
Total speed : 4476 Sol/s (MAX)

RIG02
6x MSI 1060 Mining (297-316 Sols/s)
1x MSI 1060 OCV2 (336 Sol/s) MAX
1x MSI 1060 Gaming X (320-340 Sol/s)
=> 1060 Mining cards on power limit %100 and Memory clock 4104 MHz (+100 in afterburner)
=> 1060 OCV2 on power limit %108 and Memory clock 4176 MHz (+375 in afterburner)
Total speed : 2508 Sol/s (MAX)

6x MSI 1060 Mining (271-291 Sols/s)
1x MSI 1060 OCV2 (336 Sol/s) MAX
1x MSI 1060 Gaming X (320-340 Sol/s)
=> 1060 Mining cards on power limit %65 and Memory clock 4082 MHz (+75 in afterburner)
=> 1060 OCV2 on power limit %108 and Memory clock 4176 MHz (+375 in afterburner)
Total speed : 2276 Sol/s (MAX)

Miner : ZEC Miner EWBF - NVIDIA WINDOWS Bench
Pool : Flypool

so I think 1070 is best for ZEC
I use under volt mode because i dont want to barbecue my cards just for 50 box more per year