Zwingli was appointed people's priest at the Grossmünster in Zurich at the start of 1519 and immediately did something unusual: instead of preaching on the assigned readings of the church year, he began at the first chapter of Matthew and worked straight through. Continuous exposition of a whole book became the mark of the Reformed pulpit and it started there.
The break came over food. During Lent in 1522 a printer and his friends ate sausages in the presence of Zwingli, who did not eat but defended them, arguing in a sermon that scripture nowhere commands the fast. The city council had to respond, and the way it responded set the pattern. Rather than a bishop ruling, the council summoned public disputations in 1523, at which the reforming and traditional parties argued from scripture before the magistrates, and the magistrates decided. Images were removed from the churches in 1524, quietly and by order; the mass was abolished in 1525 and replaced by a simple service of remembrance four times a year.
The principle underneath is what separates the Reformed from the Lutheran settlement. Luther retained whatever scripture did not forbid; Zwingli retained only what scripture positively required, and everything else, images, organs, vestments, the church calendar, went. Zurich's churches were left whitewashed and bare, and that austerity travelled with the tradition.