and they shall bring THE GLORY and THE HONOR of THE NATIONS into it;
Oh my, the answer to the question posed in verse 24 is found right here. The opposite of ashamed is THE GLORY and THE HONOR. While verse 24 clearly states that the kings brought THE GLORY into THE CITY, here 'they' is generally interpreted as the total populace of THE NATIONS. Now THE GLORY and THE HONOR admittedly are very spiritual items, but then THE CITY is a very special spiritual place.
On a more theological vein, some scholars point out that in order for THE NATIONS to bring THE GLORY and THE HONOR into THE CITY, they must pass through THE GATES (Jewish nation - verse 12). This may be what Zechariah's final prophesy is all about (Zechariah 14:16-21). It also explains why a country as small as Israel holds such a commanding place in world news. Even mere earthlings today sense the importance of Israel.