"Great zeal" means having a strong passion, enthusiasm, or dedication towards something or someone. It implies having a strong desire or interest in pursuing a goal or participating in an activity with great excitement and energy. Full definition
If we must go back to the Reformers, why not go to Ulrich Zwingli, who developed a popular liturgy and led the Reformation over most of Switzerland with great zeal? (religion-online.org)
Perhaps one of the best cities to stay in America, Florida too leads the lane of love as it is among the top 5 states that has shown great zeal for interracial dating in America. (interracialdatingfree.com)