OK, just ran a quick test on the current dev build. 4 standard zeds in the evac shelter. Test char (Play Now!) was a Groom with Slow Runner and Parkour Expert; I stripped him prior to the test.
Wearing/wielding non-fitted gear you described, skill 0, the raincoat was destroyed and I lost about one | of health on all body parts. Legs took a little more, one arm got dinged for \ and one arm came through OK.
Got a replacement raincoat, layered over the jacket as before. Healed the char back to full health, roughly 6 pain left. Increased Melee to 8, Dodging leveled to 1 during the course of this test, as had piercing in the test before. Raincoat destroyed, two Deep wounds (head and left leg), Head down two bars, Torso and R leg down one, L leg down 1.5, and the arms made it through unscathed.
Healed up, fitted all the gear. 4 zeds later, head’s down two notches again, and each leg is down a notch with a Deep Wound to boot. Torso’s OK.
All in all, this character would be in nontrivial trouble after the last test (that’s two clean/cauterizes there), and that’s after 4 zeds. Though you may have had gear or skills not mentioned (pants might help?), I think the zeds are more dangerous than you credit them with being.
And individual standard zombies, as used here, should NOT be a threat to an experienced character. It’s the hordes, that swamp you and constantly attack, that keep zeds scary at high levels.