I'm just about to drop the review for the iHybrid, and recently had a Zenesis in for review as well.
They seem very similar at first glance- in fact, the atomizer assembly is almost identical, down to the fact that they use interchangeable glass tank pieces (a full-size zen tank will fit on an iHy, and vice-versa). But, they function very differently.
I won't give a whole lot away, but I've gone over these both thoroughly, and I will say that performance-wise, the iHy really trumps the Zenesis in every way. There are only a few faults with the iHybrid, and none of them- NONE- are performance-related. In four years, there are no other devices I've tried that come anywhere near as close to vaping perfection.