Zudjari (or just Zudj, in their language) are humanoid in build with distinctive grey to green skin, bald, slanted heads, and a mouth that opens vertically. They are a militaristic, expansive civilization, that invade planets, consume the resources, and enslave the population before moving on; Sectoids are among the races conquered by the Zudjari, while Mutons appear to be hired muscle.
The Zudjari military technology can put the U.S. and the Soviet nuclear arsenals to shame, as exemplified by their laser and plasma weaponry, auto-turrets and Titans, but as with everything, a resourceful XCOM agent can capture their tech and turn them against the Zudjari.
The Zudjari take many active roles on the battlefield:
Outsider: The rank and file Zudjari soldier.
Outsider Elite: These hardy Zudjari soldiers sport a shield which allows them to close on unwary agent and release a deadly close combat attack.
Sniper: Snipers hold high positions on the field and deal massive damage when their shots connect. They utilize laser or plasma rifles which emit a visible red sight that you can use to see it's intended target as well as follow the sight back to the Sniper's nest. See: Sniper Elite or Rocket Sniper.
Phantom: Phantoms are close quarters combat specialists. They will cloak using their technology and close on you and your Agents attempting to flank and deal massive damage with their weapons. While cloaked then can still be seen due to a shimmering affect from their cloaking technology, mines from an Engineer class will help in countering their assault.
Scout: Scouts are dangerous close combat/melee combatants. When encountered they will use a teleportation device to jump from cover to cover around the field. They transport gives a distinguishing visual of vertical stripes of light where the Scout was (if disappearing) or where it has moved to (if reappearing). These warriors sport a shield in addition to their teleportation ability. Once their shield has been taken down they will roar and subsequently charge the player's position or that of his teammates. The Engineer's mine ability can mitigate this danger as the Scout does not use his teleporter to close the distance.
Each of these veteran Zudjari sport a personal shield to make them that much more of a threat on the battlefield.
Minion Commander: Spawn Drones which will harass the player with lift beams and heal friendly units.
Tech Commander: Spawn Turrets and will attempt to repair damaged turrets.
Shield Commander: Utilize their abilities to shield their forces around them, Outsiders and Sectoids alike.
Psion Commander: Use Mind Control and Lift abilities to deal substantial damage to you and your team.