Let me be a little necromancer here, as I do not want to open another, similarly-named thread. My question is if you can possibly stack Zephyr's Grace with Ambushes and Feints in a way you get an additional snapshot, before you shoot normally using the Ambushes and Feints special rule. Yes, I do look for cheese, because I am honestly tired of invisible 2+ save wolf stars or 2+ inv daemon-spawning hordes, so it's always good to get a nice hug from the rules, especially now that the Hunter Contingent is no longer OP.
The OP needed a little update for some of the FAQ that have come out since I posted it. Nice to be reminded
I am afraid the short answer to your question is no. Zephyr's Grace merely permits a unit to snap-fire after running, it would need to be far more unambiguously worded before most players would think it grants the unit an additional snap-shot. As a unit using Ambushes and Feints can already fire at full Ballistic Skill there is no benefit from being able to snap-fire.
The only plausible benefit comes from wanting to move multiple units into range/position and use Coordinated Firepower - Zephyr's Grace does not have the "use it immediately or lose it" restriction so if you need to run multiple units it could let you do that. Then only the last unit uses Ambushes and Feints before they all declare a coordinated shooting attack. It is a bit of an edge case.