Wiring between chimeny and brick facade
Use an EMT sleeve mounted to the back of the veneer

IRC 1003.18 requires a 2" spacing between masonry chimneys and combustibles.  Given that you have a 4" air gap between the masonry veneer and the chimney masonry, this leaves 2" of space to run the cable through.

While you could run the bare cable through there and anchor it to the veneer at each end, this leaves the cable vulnerable to a masonry fastener mishap.  A better plan is to attach a sleeve of EMT to the back of the veneer then run a length of 12-2 through it to cut-in masonry boxes on either side of this run; the sleeve will protect the cable from any mechanical damage, and the 12-2 will provide some margin for thermal derating.