Final answer:
During the Marburg Colloquy of 1529, Martin Luther and Ulrich Zwingli disagreed on the nature of The Lord's Supper (Eucharist), with Luther retaining a notion of real presence and Zwingli advocating a symbolic interpretation.
Step-by-step explanation:
In the Marburg Colloquy of 1529, Martin Luther and Ulrich Zwingli failed to reach an agreement on the nature of the sacrament of The Lord's Supper (Eucharist). Luther, the initiator of the Protestant Reformation, and Zwingli, a leader of the Reformation in Switzerland, had divergent views on this sacrament. Luther maintained a belief in the real presence of Christ in the Eucharist, a stance distinct from the Catholic doctrine of transubstantiation, but he still believed in Christ's physical presence in some form. On the other hand, Zwingli viewed the Eucharist as more symbolic and commemorative of the Last Supper, rejecting the belief of physical presence in the elements consumed during communion.