1)
Who are "Tziyim"?
1.
Rashi: They are groups of officers, like the Targum of "v'Tzim mi'Yad Kitim" (Bamidbar 24:24) 'v'Siyan Yitztarchan mi'Romai.'
2.
Radak, Malbim: They are people who dwell in Tziyah, i.e. deserts, like Kadariyim and others. Even though they are far from settled places, they will bow, and all the more so others!
2)
Who are "Oyvav"?
1.
Radak: They are those who wanted to be his enemies, but they could not. Rather, they lick the earth amidst fear of him.