With the Mathorn MB-212A Ultimate battery (Nikon EN-EL15C), your camera is ready to work under heavy loads.
4K recording and video broadcasting are situations where the camera consumes up to 5 times more power than in single shot mode with Live View mode.
You're in the right place with a Mathorn Ultimate battery, suitable for the Nikon Z8, Z6 II, and Z7 II among others.