There's lost of variations on how to set it up, but here's what I would probably do:
1. Buy two of the 12 port terminal/distribution blocks and mount underneath.
2. I would not bother with dividing your track into power blocks/districts at this stage until you see if you have any DCS communication issues once up and running. If you do, you can easily separate the loops into blocks by using a Dremel and thin cut-off wheel to cut the center rail and create your blocks. If you don not (and many do not) no need to do anything.
3. Run one handle of your Z4K to Fixed 1 IN on the TIU and then from Fixed 1 Out to the input leads of one terminal block with 14 gauge stranded wire.
4. Run the other handle to Fixed 2 IN on the TIU and then from Fixed 2 Out to the input leads of the other terminal block with 14 gauge wire.
5. Run four sets of wires from ports 1-4 from terminal block 1 to your outside loop with 16 gauge wire to the track at 4 different locations - one at each end of the oval loop and one in the middle of the front and back straights, so you've "carved" your loop into 8 about equal sections.
6. Run 8 sets of wires from terminal block 2 to the two inner loops (four wires per loop) in the same fashion as the outside loop.
7. You can make your connections from the terminal blocks to the track in different methods such as soldering directly to the track or using the male spades below. Because the outer ground rails are not tied together with your track, many people tie them together to get a solid ground connection - you're basically creating a "Y" connection. If you use the male spades, you can solder a wire to each spade, insert the spade into the bottom of each outside rail and then each wire down through the layout and join the ends together with the ground wire coming from the terminal block port to this particular connection - you can solder all the ends together, use a wire nut, connector, etc.
That set up should get you sufficient power and DCS signal strength to all of your loops, but if you find that you need more power, you can run more connections from your terminal block ports to the track or if you put your sidings on separate toggle switches.
I'm not sure if you plan to isolate your loops from one another.
You can then use the 10v and 14v taps on the back of the Z4k to power your accessories.
