Everyone knows my take on calories before sleep and I'm not a fan of inefficient protein sources before bed either. I personally take my last protein shake (which has zero casein) about 2 hours before bed and my BCAA's about 30-45 minutes before Somnidren-GH and ZMK. I find this to be the optimal timing for my body.
I would say at the very minimum allow 60 minutes between ZMK and your casein. Or take your casein first and then ZMK an hour after that.
Most casein protein sources mix micellar with calcium caseinates. They usually yeild 450-600mg of Calcium per serving which is enough to negate the desired effects of ZMK. Since the casein takes so long to digest (5-7 hours for most) there is no need to down it right before bed imo.
I like nelix's regimen too. Only I'd add B-6 so my ZMT ingredients worked better.