Wiring DJM750MK2 with XDJ1000mk2 for rekordbox

Equipment used:
- DJM750MK2
- 2x XDJ1000MK2
- MacBook Pro
- Rekordbox
Drivers all up to date

Following problem:
Somehow I have a bad feeling during my cable setup. At first I thought to use the whole system and record box it is sufficient to connect the XDJ with the DJM via cinch cable and connect the DJM (has integrated sound card) with a USB cable to the Macbook to control everything with recordbox. However, I did not get it started using this cabling method. The XDJ are not recognized by Rekordbox.
With the settings in Rekordbox appears as audio output only the Macbook internal Built in Output although I installed the drivers of the DJM recordbox does not list the soundcard of the DJM. Also in the system settings of the Mac it shows me the DJM as audio not. Funny thing is that I could set the driver software from the DJM. As soon as I change the channels on the mixer (Line / Phone / USB), the change in the driver software is immediately visible. I first thought the sound card from the DJM is the problem as soon as I remove the USB cable while using Rekordbox shows the software briefly to the DJM was removed.

Solution:
I then started to connect the XDJ directly via USB cable to the Mac (without USB connection DJM to Mac) and they were both detected. After I installed the aggregator tool I was able to select the XDJ without problem in the audio settings of Rekordbox and the system is now running.

I would be glad if you let me know if the attitudes are correct or they are wrong. The instructions I have read up and down but found nothing purposeful, except that in the DJM instructions an image is clearly visible on the is that the DJM via USB to connect to the computer (which has not worked for me as described above ).