What will be known among the Goyim?
Radak: When they will go in the Goyim's land for enjoyment or business, even though they do not need [to leave for business], they will be known and recognized for their great honor and grandeur. They will go in garments of freedom and embroidery.
Why does it mention "Zar'am v'Tze'etza'eihem"?
Radak: These are the youths, who go amidst desire to see lands of Nochrim.
Malbim: Not only Zar'am (their mature children) will be renowned - also Tze'etza'eihem (minors).
Why does it mention "Goyim" and "Amim"?
Malbim: They will be renowned not only among Goyim (lowly Nochrim), rather, even among esteemed Amim.
What is the significance of "Zera Berach Hashem"?
Malbim: They will be recognized for being awe-inspiring.