The Gospels are four separate biographies. They are independent.

Except they are not. When three texts are about 50% identical, there's a very low chance that they are fully independent. This has been known by biblical scholars for decades now.

There are also references to Christ's crucifixion by the historians Josephus and Tacitus.

Who are talking about what people were saying at the time. A news article about scientology does not prove that scientology is true.

Being written within decades of his life is considered EXTREMELY good for ancient historical manuscripts.

Except that the gospels are not historical manuscripts, they are specifically written to convince people of a story. Historians don't write to try and convince their readers of what they say, they try and report the facts as best they can. This is just plan not what happened with the New Testament.

The authors of the Gospels were tortured and killed for refusing to renounce their beliefs

That's a very popular tradition, but holds very little historical truth. Statements about Christian persecution were either widely exaggerated or fabricated out of whole cloth.

You don't have to consider anything reliable, we are just asking you to back up your claim that the evidence for Zeus is the same as the evidence for Christianity. This would be very difficult for you, as the historical evidence for Zeus - outside of clearly literary sources like the "Iliad" - does not exist.

Some people have had personal experiences with Zeus, and know within their hearts that Zeus is real. I'm not making this up. There were historical documents written about the actions of Zeus at various historical events, like the Battle or Troy, and how he was the father of Hercules. Why do you think people would have made that up if there wasn't very good and convincing evidence that it was true?