How religious was Paul before his conversion compared to other Jews?

Les explains that Paul’s past was that of a religious Jew par excellence, a law-keeping Jew and religious zealot the likes of which no one else could come close to. He even killed people because they were accepting something contrary to the law. He was a great practitioner of Judaism and thought the law, the temple, and the Old Testament were the epitome of everything. But when he realized all of that counted for nothing because the work of the cross had become preeminent, and salvation is only through faith in the finished work of the cross, he refused to rebuild what he had torn down. If he put converts back under the law and commanded circumcision, he said he would make himself a transgressor.