What are the themes in the categories of Zakat?

The categories of Zakat can be divided into three categories considering the purpose which they serve:
Poverty relief and economic empowerment – this incorporates the first (the poor), second (the needy), fifth (those in bondage), sixth (those in debt) and eighth (travellers in need) categories of Zakat.
Causes for Islam – this incorporates category four (those whose hearts need winning over) and category seven (for the cause of Allah) of Zakat distribution.
Zakat management – this incorporates category three (administrators of Zakat)