Philip Schaff, History of the Christian Church: Volume 8, The Swiss Reformation, The Protestant Reformation in German, Italian, and French Switzerland up to the Close of the Sixteenth Century, 1529-1605 (Peabody, MA: Hendrickson Publishers, Inc., 2002 [orig pub. 1892]): §9, 34-6.
The training of Zwingli for his life-work differs considerably from that of Luther. This difference affected their future work, and accounts in part for their collision when they met as antagonists in writing, and on one occasion (at Marburg) face to face, in debate on the real presence. Comparisons are odious when partisan or sectarian feeling is involved, but necessary and useful if impartial.
Both Reformers were of humble origin, but with this difference: Luther descended from the peasantry, and had a hard and rough schooling, which lefts its impress upon his style of polemics, and enhanced his power over the common people; while Zwingli was the son of a magistrate, the nephew of a dean and an abbot, and educated under the influence of the humanists, who favored urbanity of manners. Both were brought up by pious parents and teachers in the Catholic faith; but Luther was far more deeply rooted in it than Zwingli, and adhered to some of its doctrines, especially on the sacraments, with great tenacity to the end. He also retained a goodly portion of Romish exclusivism and intolerance. He refused to acknowledge Zwingli as a brother, and abhorred his view of the salvation of unbaptized children and pious heathen.
Zwingli was trained in the school of Erasmus, and passed from the heathen classics directly to the New Testament. He represents more than any other Reformer, except Melanchthon, the spirit of the Renaissance in harmony with the Reformation. He was a foreruner of modern liberal theology. Luther struggled through the mystic school of Tauler and Staupitz, and the severe moral discipline of monasticism, till he found peace and comfort in the doctrine of justification by faith. Both loved poetry and music next to theology, but Luther made better use of them for public worship, and composed hymns and tunes which are sung to this day.
Both were men of providence, and became, innocently, reformers of the Church by the invisible logic of events. Both drew their strength and authority from the Word of God. Both labored independently for the same cause of evangelical truth, the one on a smaller, the other on a much larger field. Luther owed nothing to Zwingli, and Zwingli owed little or nothing to Luther. Both were good scholars, great divines, popular preachers, heroic characters.
Zwingli broke easily and rapidly with the papal system, but Luther only step by step, and after a severe struggle of conscience. Zwingli was more radical than Luther, but always within the limits of law and order, and without a taint of fanaticism; Luther was more conservative, and yet the chief champion of freedom in Christ. Zwingli leaned to rationalism, Luther to mysticism; yet both bowed to the supreme authority of the Scriptures. Zwingli had better manners and more self-control in controversy; Luther surpassed him in richness and congeniality of nature. Zwingli was a republican, and aimed at a political and social, as well as an ecclesiastical reformation; Luther was a monarchist, kept aloof from politics and war, and concentrated his force upon the reformation of faith and doctrines. Zwingli was equal to Luther in clearness and acuteness of intellect and courage of conviction, superior in courtesy, moderation, and tolerance, but inferior in originality, depth, and force. Zwingli’s work and fame were provincial; Luther’s worldwide. Luther is the creator of the modern high-German book language, and gave to his people a vernacular Bible of enduring vitality. Zwingli had to use the Latin, or to struggle with an uncouth dialect; and the Swiss Version of the Bible by his faithful friend Leo Judae remained confined to German Switzerland, but is more accurate, and kept pace in subsequent revisions with the progress of exegesis. Zwingli can never inspire, even among his own countrymen, the same enthusiasm as Luther among the Germans. Luther is the chief hero of the Reformation, standing in front of the battle-field before the Church and the world, defying the papal; bull and imperial ban, and leading the people of God out of the Babylonian captivity under the gospel banner of freedom.
Each was the right man in the right place; neither could have done the work of the other. Luther was foreordained form Germany, Zwingli for Switzerland. Zwingli was cut down in the prime of his life, fifteen years before Luther; but, even if he had outlived him, he could not have reached the eminence which belongs to Luther alone. The Lutheran Church in Germany and the Reformed Church of Switzerland stand to this day the best vindication of their distinct, yet equally evangelical Christian work and character.