The lowest I've ever seen them were 1.8Ω, these will work. Personally I like them at 2.2Ω - 2.4Ω. But with a Zmax and it being variable wattage, any ohm that is not below 1.3Ω should work fine.
Vivis come with three heads - 1.8, 2.4, and 2.8 ohms. I've found the 2.4 ok, and the 2.8 optimal with the Zmax. It works better with those. A 1.8 ohm isn't really necessary on a vv/vw mod. Provape give the same advice actually, for the same reason:
"Low resistance atomizers/cartomizers are not the best to use, they will limit the voltage options that you can go up to. Also note that as a atomizer heats up, their resistance drops. When they get dry the resistance also drops. If you have your voltage set higher and the resistance drops, it will cause the E1,E2 errors."
That's for a different pv, but the principle is the same.