In the root of your micro SD card must be a folder called "local", as you have, the zImage file named "zImage" and the "rootfs" file. Then switch on the Dingoo and hold the select button pressed until you see the penguin on the screen, then it boots into Dingux. Of course only if you did everything right with the dual boot install.

Can't remember which message I got when the Dingux install successfully finished?