Simple solution - ride more. Most of us here are so far off the actual curve of fitness that any level of activity is likely to be pretty productive in burning fat and improving the other areas you're looking at. I tend to simply ride however fast it feels comfortable to do so on any given day. This morning that was ~18mph, other days on this same ride I've very comfortably cruised at 20mph. So bascially, until you get to the point where you feel like your level of fitness has plateaued you probably don't need to worry much about zones IMO.