How do i capture a Zaptos?

You can catch it without a master ball but it takes a lot more time and luck to do. First, save right in front of it before you start the battle. When you're fighting it, try and knock its health down to the very lowest it can go so the red health bar is barely visible. Then try using Ultra Balls continuously on it until you get it. It might take a few tries, but it definitely isn't impossible. Hope this helps :)