Help with hitting

Hi everyone,
I play volleyball and I’m fairly tall (1.81 m / 5'11"). I’m an opposite hitter. My hitting is powerful, but I often either hit into the block (sometimes I hit so hard that the ball breaks through) or into the net because I’m trying to drive the ball down too steeply.

I have good timing, coordination and I jump quite high, so I contact the ball well above the net. But then I tend to “bring it down” too much. My coach tells me that if instead of trying to hit it straight down I would extend my arm and drive it deep, I’d have some huge shots. He keeps telling me to “lengthen” my swing but I’m not sure how to actually do that.

Any tips, drills or cues to help me extend my swing and hit deep instead of straight down?