This was all first discussed in the admin section before I even made the changes so we could ensure there would not be major issues when the system went live. This thread explains what is going on for regular users.

On escape maps the Health and Damage to zombies has been scaled up. The new health values are 8 times what they were before and the damage is 9 times what it was before. This represents a 12.5% increase in all damage.
Knockback was decreased by 9 times so that it is scaled with damage. Regen has been dramatically increased.
Previously zombies regenerated hp very slowly and only if they were not taking dmg and even then only got effectively <0.03% hp gain per second if not taking any damage for intervals sometimes lasting as long as 15 seconds. Now zombies Regen at a rate of about 0.25%hp per second at all times and spawn with a nade that will regen 10% of any zombies who are in the AOE for 4 seconds. Zombies regen faster when at very low HPs.
Zombies speed now is a ratio to their HP where as a 10% decrease in HP will result in a 5% decrease in speed and no zombies speed will be set below 0.6 by this system. In addition the system now attempts to enforce the correct speed values for zombies on all escape maps so we do not have deformed running at the same speed as fast zombie on shroom.

So here is the take away points:
  • Humans deal 12.5% extra dmg on zombies
  • Knockback reduced 12.5% to compensate
  • Zombies regen HP between 8 to 50 times the previous rate
  • Zombies speed is correlated with a players HP in a linear function decreasing at half the rate of their hp changes and with a floor of 0.6
  • Zombies speed should be now the correct class speed when a zombie spawns instead of whatever a map tries to enforce.