Paul as always passionate. Everyone is. The question is always what are you zealous for? What is your passion? Paul's pre-Christian passion was for human traditions. Things passed on from one generation to another. The same kind of traditions no doubt that Jesus critiqued in Mark 7v8-10,
"You leave the commandment of God and hold to the tradition of men... You have a fine way of rejecting the commandment of God in order to establish your tradition! ...making void the word of God by your tradition that you have handed down. And many such things you do."There is good tradition, which is to keep holding to the word of God, but they devised traditions that emptied and opposed the word of God. That was the self-justifying approach of the Pharisees, powerless against sin and able only to provide external change.
Then Pharisee Saul's passions changed when Jesus revealed himself. As he says later in the letter - "It is fine to be zealous, provided the purpose is good, and to be so always and not just when I am with you" (4v18)
Zeal, like faith, is something we all have.
The question is what is the object of your faith?
What is the object of your zeal?