TheDZ2500 is the "not so simple" controller.
The device that you want to use is designed to supply voltage from what I read. That's what will eliminate the DZ controller.
I took a quick peek at the instructions for the device. It appears that you have to choose a mode to configure it to operate whatever you are controlling. Then, that configures which ports you will use. Then, each port will be assigned a DCC code to address for operation.
it appears that you would follow the DCS/2 wire Mode to connect to the ports on the 51820. (see attached)
I don't do DCC, so I was only skimming the manual for that side.
You do grasp that the 2500 motor is not a snap, but a slow move of points that would need to be controlled by 51820 at the proper DC voltage.