Romans 10:2 - 3
ESV - 2 For I bear them witness that they have a zeal for God, but not according to knowledge. 3 For, being ignorant of the righteousness of God, and seeking to establish their own, they did not submit to God's righteousness.
1st century Isra'el’s zeal for God was not according to knowledge, because instead of accepting Yeshua (Jesus) as the means of salvation, they sought to establish their own way—which was a “two-sided” coin. Their errant belief taught that 'side one' of the coin, salvation, was grace-based due to birth (ethnicity and group membership in Isra'el as Jews); and that side two, remaining saved, was based on maintenance of Torah (viz, obedience). In that order, both were needed in the Jewish mind for salvation (read Acts 15:5 – “circumcise them”=Jewish identity, and “Law of Moses”=maintenance of Torah).