Welcome to the ROG forum.
When running high capacity/high speed ram such as yours, it comes down to if the cpu's memory controller or motherboard can handle it.
You have Samsung TridentZ Royal 64GB at 4266MHz, that's asking a lot in my opinion but it seems you're getting close and may have a chance to get there.
You're likely going to have to raise some voltages, I see XMP sets Dram voltage to 1.50v
Dram voltage - 1.55v
CPU VCCIO voltage - Up to 1.30v
CPU System Agent voltage - Up to 1.30v - 1.35v
These would be the maximum voltages I'd try. If you can't get 4266MHz stable, you may have to settle for a lower speed or try 32GB with two sticks.