Muza in quite a few east european languages means "Music". By inference, I get to the book of Psalms in the Old Testament. "Psalms" literally means 'Songs'. Psalms 25:19 reads: "Consider mine enemies; for they are many; and they hate me with cruel hatred."
This could go either way, talking in a 'current' context, this graffiti appears at the door where Smith knocks, behind which are the many captains of Zion, these are his many enemies. Alternatively, this could be a 'future' reference to Neo's many many Smiths that he later fights.