What do we learn from "Yehalelcha Zar v'Lo Ficha"?
Malbim: What a person praises himself is not praise. It is good to do deeds proper for praise, to the point that someone else will praise you.
Here it says "Yehalelcha Zar v'Lo Ficha." Ovadyah said "your servant has feared Hashem from his youth" (Melachim I, 18:12)!
Nedarim 62a: One may state his merits where he is not known, but not where he is known.
Why does it mention Zar and Nochri?
Malbim: Nochri is someone from another land. After a Zar (stranger) will praise you, even a Nochri who does not know you will praise you. He will hear from the Zar and publicize your praise.
What do we learn from "v'Al Sefasecha"?
Malbim #1: The Al (refraining) of your lips [from praising yourself], this itself praises you. It shows the Midah of humility and an attribute.
Malbim #2: The lips are more external than the mouth. People will not hear your lips lower yourself, and say that you lack this praise. A Chacham may deviate about three matters (Bava Metzi'a 24a; one of them is denying that he knows a tractate, amidst humility). Also this will be praise for you!
