IMO, we should user defend everything... it's the only way to be sure that your defenders do what you want. It's easier to accept bad defense if I screw up the play than if the CPU screws it up. I always switch to defend (if needed).
That said, the Streak/Corner route combination requires a Deep Third zone with a Buzz Zone underneath. If there's no receiver in the flat, don't bother covering it. Buzz that curl defender instead.
If there is a flat, corner, streak combo... Use a CLOUD coverage which has a flat, buzz, and a deep zone.
Also, don't underestimate the value of customizing your coverages to attack your opponent. If they want man, give it to them, but zone the areas they throw the ball.
A man defenders with a buzz defender will certainly take the corner route away (setting you up for something else).
Later