Noah didn't underestimate Zach, but Gil and Bertha's abilities were far more annoying in that situation. Gil could track him down even after months passed, and Bertha's attacks carried a massive amount of power.
It was a simple matter of necessity. Dealing with Zach's abilities wasn't a priority in that situation, but that still made him feel underestimated.
Zach's aura became more intense. The smell of blood became more intense in the area, and more parts of the environment transformed into weapons that flew toward Noah. Pieces of his skin also separated from his body to take the shape of dark-red spears that joined the offensive.
Gil was sure that he would die if he remained in that position. A different howl came out of his body and made his figure disappear.