What is the meaning of "Mi Yatzar El"?
Radak: Who forms a god - an act of Tohu like this?! He toils for nothingness, and puts his silver for folly - is there lunacy like this?!
Malbim: Who does such a folly, to form a god for himself, after he sees that it does not help?! One who does something lowly, he should get a big benefit to justify the shame he bears. Does someone make an idol without benefit?!
What is "Nasach"?
Rashi: It is an expression of Yetzikah and Masechah (pouring melted metal to make a molten image). The Nun [in Nasach] is omitted in some forms of the word, like the Nun in Nashach and Nagaf.
Radak: He covered [the idol with silver and gold].
Malbim: "Mi Yatzar El" corresponds to idolaters who think that the idol has divinity. "U'Fesel Nasach" corresponds to idolaters who think that the idol draws influence from a star that loves its form.