Husseini did not command any units. His role was strictly to serve as an ambassador to Balkan Muslims to encourage them to join the various SS units set up by the Germans. In particular, he was important in urging Bosnian Imams to get Bosnian Muslims to join the SS Handzar unit.
The Handzar unit was not at all involved in the rounding up or murder of Jews, but they did slaughter Serbs.