You have to remember that the Zen devices, like ZAP, ZAU, etc., came along before the more recent sub ohm craze. The ZAPs came equipped with an insulated wick hole, ridiculously skinny wick, and a pre wrapped, 2.0 ohm coil with 32g wire. They worked reasonably well, for what we knew at the time, on a Provari. That original build still does, at least in comparison to Pro Tank type devices. In videos and on forums, Zen (Mike) himself was adamant about using no heavier than 32g wire.
Since those original Zen builds, fatter wicks, heavier wire, and lower resistance became more popular. People began removing the wick hole insulator, rolling bigger wicks, and wrapping coils with lower resistance. Provari obliged, somewhat, by increasing the maximum amperage cut off to 3.5, from the original 2.5, and lowering the minimum voltage from 3.3V to 2.9V. This allowed a theoretical resistance build down to about .8 ohms. But the resulting wattage, before the maximum amp limit is reached, is less than 10 watts. Not really adequate for todays big wire, fat coil, sub ohm builds.
I guess my point is, the ZAP is a very well made device. Machining is second to none. The quartz tank is the best you can get. But, on the whole, the ZAP/Provari set up is somewhat dated.