it's usually an internet error, you may have disconnected from the internet while it was downloading. Download on a reliable internet service. Let me know if it helps. : )
you can't use archive utility to do it. Download The Unarchiver from the app store. Then, before unzipping, right click and click on the unarchiver. It will unzip a app and you can move that into applications folder.
You have to carry this heavy burden on top of you, and when you hit something bad the burden on your shoulders increases. With that, the fall speed (gravity speed) increases, and it is hard to move up, left, and right. (I was going to make this, but I quit the jam.)