I just got a new HP PC with a Skylake processor and can't get Vegas Pro 13 to work with Quick Sync, it says Quick Sync isn't available although Handbrake can use it without problems.
On my i7-3770(k) system, Quicksync saved me 2 seconds in 64 seconds and left me with this. I hope you have better luck. I've been running CPU only for quite some time.
I also have an Intel 3770K. I have no problem with Quicksync for 720P renders from Vegas. However, 1080P does not work. Sometime back, Sony acknowledged the problem but has not fixed it. I now use the one-click Vegas to Handbrake method of encoding. Quick sync works without issue and is roughly twice as fast as CPU only. The avisynth script used by Vegas to Handbrake can even be optimized to increase Quicksync encoding speed. Most of my renders are 1080 60P. Quick-sync also works for TMPGEnc's Mastering Works 6 without issue.
There have been other posts on Quicksync here and on the Creative Cow forum. They might have some suggestions on things to try.
A tutorial I saw showed that Vegas needed to be running on the Intel display adapter as primary monitor (1) in windows. Other monitors on discrete GPUs would be 2,3,4. Most monitors will have multiple inputs, and so hooking the intel display interface up to a second monitor input works as well.
There isn't any way to set the primary GPU in the BIOS, it can only be turned on and off.
Vegas shows an option for using the intel GPU for rendering, but that's not the same as Quick Sync. I'm beginning to think that Vegas just can't use the Skylake QS even though Handbrake works very well.