This spell creates an undead servant. A zombie that can follow complicated instructions.  A zombie that has greater health and attack. Can raise three basic zombies of its own that directedly follow its orders. can only have one zombie commander at a time 

On each of your turns, you can use a bonus action to mentally command any creature you made with this spell if the creature is within 60 feet of you. You decide what action the creature will take and where it will move during its next turn, or you can issue a general command, such as to guard a particular chamber or corridor. If you issue no commands, the creature can make its own attack against hostile creatures. Can think for itself and will move to were it will think it is most needed.

The creature is under your control until dispelled or destroyed. 

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, The zombie commander can raise more undead every 2 levels higher then 4th, also every level after 3rd the zombie commander gains 1d6+2 more health, added on to its original 40 health.