From a high level view and based on what Hot Chips slides revealed, Zen is somewhere in between SB and Skylake when core resources are in question (closer to Skylake in integer and closer to SB/IB in FP). I bet the IPC will end up right in the middle of these two and from AT we know the gap is around 25%. So if it was to end up in the middle of that range or a bit lower (around 10% faster than SB) it would end up being: 1) just a tiny bit faster than IB (~4%) ; 2) 7% slower than HSWL; 3) 10% slower than BDWL ; 4) ~14% slower than Skylake (funny enough the int/fp schedulers in Zen are ~15-20% smaller than Skylake's and right at Haswell level).
The amount of time Intel has spend tweaking its cores will win out. I doubt execution resources and IPC can be directly compared like that - AMD will need more resources to achieve a given IPC relative to Intel simply because this is their first version of Zen compared to how many iterations of Core. (Intel has extracted small, but measurable performance increases across their ticks, despite allocating nearly no additional hardware resources).