DJTT just responded on Facebook again. Unfortunately none of their solutions provided earlier seem to work. Imma open a support ticket to NI...

Sadly, after re-checking both recommended workarounds it seems both will have issues with your setup.

1. Aux cable - Apple replaced the old combo jack with the same one used in iPhones in Retina models, disabling the Line Input functionality.
2. Soundflower - Getting audio into Quicktime isn't really an issue. What is tho is that you'll have to aggregate both Soundflower and the Z2 as a new device so you can have both working in Traktor. Since you are using timecode, Traktor will disable timecode since that aggregated device is technically not DVS enabled hardware, rendering this workaround useless for you. There MIGHT be a way to make it work but it could lead to instability so you'd be better off just using Traktor's own recorder and then splicing it with the video.

I noticed Patch replied to you on the forums suggesting a THRU setting but, unless it got added recently, isn't on the Z2's control panel, it's controlled by the orange Traktor buttons on the top of each of the mixer's channel so if those are lit THRU should be technically disabled already.