There isn't any way to fix it unless the cracks are contained in the very top layer. Polyester resin doesn't like to be in the sun a lot, and it's prone to shrinking and drying out, which is why it's cracking. UV light is very damaging to polyester resin, which is why I laugh when almost every company out there makes their hoods out of polyester resin.
But, if the cracks are from an impact, you're equally screwed. I wouldn't worry about the cracks unless you care about cosmetics, and if so, paint it. Or get a new hood, get a better one this time, and get it clear coated with a UV inhibitive clear coat. The key is protection, you're already too late to do anything about it.