Wiktionary
vb. To unzip
Usage examples of "zip down".
I'll have to pull my zip down pretty soon or I'll leave a big wet spot on my fly.
She needed that hope now as she saw Josh's car zip down the road and swing up the snaking drive.
She undid the button of her jeans and eased the zip down, untucking her crimson jumper so that no one would see.
This should give you something to think about as you zip down the highway next summer.
With each sentence he got closer to me, until at last he was pulling the zip down the back of my dress.
He leans over me, puts his big fingers to the zip of my jeans and starts trying to pull the zip down.
Then I saw the blood: it had started dripping from the edge of his padded jacket, and when I pulled the zip down I saw it had been pooling inside, black in the moonlight, soaking.
She watched Ute zip down from the east corner on a compact jet-bike.