I won't say proof, but there is evidence outside of the bible. I see here many people saying that there isn't which is a blatant lie. Now maybe they don't accept the evidence given but the fact is there are many writings that refer to Jesus.

1. Gospel of Thomas (not in the bible)

2. Gospel of Judas (not in the bible)

3. Flavius Josephus

4. The Quaran

5. The Jewish Talmud

6. Roman historian Tacitus

7. the Baraia (Jewish)

8. Sanhedrin (Jewish)

9. Gospel of Peter (not in the bible)

10. Gospel of Mary (not in the bible)

11. Secret Gospel of Mark (not in the bible)

12-37. 26 books of the new testament

There are also other references to Jesus in other gospels that are referenced in writings but to this date have not been found.

We also know of 2nd century writings that attack Jesus and his charachter or intentions but do not make the claim that he never existed

1. Celsus, a pagan philosopher

2. Lucian of Samosata

None of these essentially prove that Jesus existed but it seems to me that it would be a large leap in logic to just suggest that these are all made up and Jesus never existed. I listed 39 writings (including the new testament) that mention Jesus and none of them claim he never existed. All of them were written before the end of the 2nd century.

There is plenty of evidence that Jesus existed, It is up to you to decide whether or not to believe it as truth or to dimiss them as if they were all made up.

Try to find that kind of information about Zuez, Mithras or any other God outside of Judiasm and Islam. All you can find is explanations of their story and not the actual writings that basically invented them as you would say about the bible inventing Jesus. So it is a big difference to believe in Jesus/ Abrahamic God than it is to believe in the other mythological gods. So it's hard to say that Jesus is just another made up God.