It's busted lines might be a bit confusing to understand. It's here should be understood as it has, busted can mean broken open or smashed, and lines can be understood as cracks. Thus, we might interpret the sentence to mean that smashing the coconut has caused it to have cracks along its surface, thereby making it easier to open.
Ex: The coconut shell was cracked and had many lines running along its surface.
Ex: The man easily busted open the coconut shell.