Murmured - Found fault, complained.
To be a guest - To remain with, or to be entertained by.
A man that is a sinner - All publicans they regarded as great sinners, and the “chief” of the publicans, therefore, they regarded as especially wicked. It would appear also from Zacchaeus’ confession that his character “had been” that of an oppressive man. But the people seemed to forget that he might be a penitent, and that the Messiah came to save that which was lost.