Error in Greek Mythology

[Athene]

I forgot to, but I realized that in greek mythology, there's a big error. So, apparently Hera had Hephaestus by herself since she got mad at Zeus for having Athena, since she either forgot he swallowed Metis, or didn't know. But, Hephaestus chopped open Zeus's head for Athena to be born. How is that possible?

[Orion]

Er- what's the problem with Hephaestus chopping Zeus's head open? And Athena hadn't been born when Hera decided to have a kid all by herself, she had just found out, like she always does, that Zeus had been seeing Metis, and also knew she was pregnant. Afraid of Hera, Zeus swallowed Metis, who gave birth to Athena in there and then dissolved into thought, while Athena went to her dad's head and started kicking it open, resulting in serious headache, so he asked Hephaestus, who had been called back from his exile by Dionysus, to chop his head open.

[Fritz]

It's mythology. These stories, deriving from various Ancient Greek writers, often conflict. Not all accounts state that anyone cleaved Zeus' head open and of the ones that do claim it, not all of them claim it was Hephaestus. Gotta take it all with a grain of salt and pick the versions you want to go with.