We do not insult Mary, the Virgin Mother of God, when we forbid that she be adored with divine honors; but when we would attribute to her the majesty and power of the Creator, she herself would not permit such adoration. For true piety has one and the same character among all men and is the same in all, because it originates by one and the same Spirit.
It cannot even be imagined, therefore, that any created being should at the same time be pious and suffer the worship due the Deity to be offered to himself. So also the Virgin Mother of God will as much the less accept the worship due the Deity as she is high above all created beings and reverently devoted to God, her Son. It is a mark of insanity in godless men and demons when they allow divine honors to be paid to them.*
Zwingli wrongly believed that Mary remained perpetually a virgin. But he was right to excoriate worship of her. Something as a Christian he simply could not and would not do.
*H. Zwingli, The Latin Works of Huldreich Zwingli. (W. J. Hinke, Ed.) (Vol. 2, p. 239).