Alma 43:6

And now as the Amalekites were of a more wicked and a murderous disposition than the Lamanites were, in and of themselves, therefore Zerahemnah appointed Chief Captains over the Lamanites, and they were all the Amalekites and the Zoramites.

The Amalekites were more evil and liked to kill more than the Lamanites did. So Zerahemnah made the Amalekites and Zoramites the captains over the Lamanites.

The Amalekites were more violent and bloodthirsty than the Lamanites themselves, so Zerahemnah put Amalekites and Zoramites in charge as chief captains over the Lamanite armies.