Certainly possible, but the Di2 wire is tiny. By the time you've hearshrunk it to a brake hose/cable it virtually disappears. Even on my bike with a straight 1 1/8" steerer and lugs, the Di2 wire is barely visible. You don't need a 44mm headtube for that.
Surely there's not going to be enough space between a ZS upper race and the steerer? Unless you thread the brake hoses through the bearing.