How to carry as Zed?

sigh I hate I have to make a discussion about this. Some reason I can't carry with Zed recently, I have no idea why. Most of the time I win lane (KILLS-WISE), but what am I supposed to do to carry after that? I can't make picks because there's always someone there to save them, and I always ward but it's never enough to stop them from screwing up my ult engages and any chance of getting a kill. So what am I supposed to do? There's 0 opportunity to pick anyone off from my perspective. I can't just engage on someone blindly because there will always be someone there, but if I do engage on what I find a good pick, they're always there. Always. I don't know what the hell I'm doing wrong.

I would analyze my play, but there isn't any program for mac users to record their games... all of them are PC only. -_- I doubt it would help me anyways.