Think I could get you to past your image into a post? The firewall I am on prevents me from accessing it. You can paste an image into a post when you use firefox.
The JTAG pins are just that, JTAG. If you are intending to hook into something needing SPI, then you will need to wire your device into a PMOD or similar as those are the only access to IO. JTAG pins on the Zynq are special in that they are just that - JTAG only.
If you want to loop the JTAG through the ZedBoard, you can, but the Zynq on the board cannot "READ" the JTAG from the other board. Each of these two boards will end up sending their data to the JTAG device attached to your PC.
I have an ADC evaluation board I would like to connect to the Zedboard via the JTAG port (connector "a" in the picture below - circled in red). Will then extract ADC data via SPI. Does anyone know if this is possible? I can't seem to find a connector to the JTAG port in Vivado block diagrams.
Zedboard image -> http://imgur.com/p00QnVg
ADC board datasheet (output is via 14-pin JTAG) -> http://cds.linear.com/docs/en/demo-board-manual/dc979af.pdf