There are many ways you can do what you want, and the flexibility of how you can arrange your zones and categories is great in AC.
In my experience, the last unit in your hierarchy should be your zone, and one of the above (usually the preceding one) your category, because usually the higher units can be scheduled to include lower levels more easily (in contrast to trying to exclude upper levels), so your zones would work like this:
1.0 PRIVATE AREAS (schedule)
1.1 Low density residential (schedule)
1.1.1 Phase 1 (Category)
1.1.1.1 Lot 1A (zone with zone#)
1.1.1.2 Lot 1C (zone with zone#)
1.1.2 Phase 2 (Category)
1.2 Medium density residential (schedule)
1.3 High density residential (schedule)
1.4 Commercial (schedule)
2.0 COMMON AREAS (schedule)
2.1 Streets & roads (schedule)
2,1.1 Paved area (zone)
2.1.2 Sidewalks and curbs (zone)
2.2 Public green space (schedule - that includes sub zones)
2.3 Institutional (schedule - that includes sub zones)
I've actually used this in practice (but with fewer levels) and it works for the partials and totals, per level and parcel total. The key is to keep every zone, well... er... individual, and use schedules to group them.
I also suggest you keep your schedules as simple as possible, and publish to .xls or something like that; and use the data as reference. You change something, publish again and just update. Then in excel work out the data (filters, etc) to get any partials, subtotals, etc. you struggle to get from AC schedules (which can be done).
The data in the attached was divided based on lot size, and included street, comercial, park & recreation, and others, in subtotals and totals; using the techniques described.
Hope this helps. Best regards.