Risk and reward come hand in hand.
Killing the undead slaves of the necromancer would alert the necromancer to his position. However, it will also be advantageous in the long run. Even if Zephyr disregarded the long-term prospects, just the loot from the undead was good enough for him to take the risk.
For example, after killing Gale, Zephyr obtained the sword he used, the mask, and the armour. The armour was too heavy for him to use in its entirety, but he still wore the chainmail to enhance his defence.
Besides all that, there was also one more thing he could have looted from the body, but didn't because he respected the man.
That was Gale's mana core.
Usually, when any magical creature dies, the mana in its body rapidly crystallizes to form a mana core. In the case of knights like Gale, their mana heart will be the location where the crystal forms.
If Zephyr wanted, he could have dug out the mana core before he buried the corpse.
However, he didn't.
