Official comment
You'll need to subscribe to the Core or Creative plans for rekordbox to unlock DVS functionality, then you can follow the guide here for instructions on setting things up.
I just picked up a XDJ-XZ. I also have two Technics 1210GR's. I want to use Rekordbox DVS with the turntables on channels 3 & 4. How is this accomplished? I can't find anything online regarding this.
You'll need to subscribe to the Core or Creative plans for rekordbox to unlock DVS functionality, then you can follow the guide here for instructions on setting things up.
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I left one piece of info out. I actually bought an interface 2 days before purchasing the XDJ-XZ. An online subscription shouldn't make a difference. I have DVS activated already.
Ah, that will make things a bit different... let me pull those out and give you some additional steps to getting things configured.
I would greatly appreciate it!
The goal is to be able to play all my music through either the XDJ and my 1210's (1210's using DVS of course)
Good news - just connect the IF2 via USB, but keep the audio device set as the XZ and your DVS functionality will be maintained with the audio connections into the XZ itself.
So I tried that. I believe everything is correct with what you're saying. However still not working. I attached a pic of what I believe is the way you described to set this up. (I'm visual) I'm using a MacBook Pro, which I doubt is an issue. I may not have my software configured right as well.

No - the only thing connected to the IF2 is the USB cable; that acts as the DVS unlock for the software, which gives the XZ the ability to use its inputs and outputs. If you did it the way you outlined it, you'd need to go through nasty configurations for the audio outputs because then you're using the XZ not as a controller, just as a mixer.
Connect the turntables directly to the XZ.