It is nice to see that finally a computer game picked up the idea to let zombies burn down to skeletons as I never forgot the utterly surprised faces of the players at our table as we used that in our self made paper game in the 80's.
Those faces were priceless smile

I just have a small idea to make this feature not a victim of the routine issue seen that, done that category as nothing is more deadly in games paper or computer games then lack of variation to break the quickly setting in routine.

I suggest simply to use the zombie-skeleton effect not every time they are set on fire but that there is a chance which can vary by the amount of fire damage done to the zombies that they can get burned as zombies to ashes or turn into smouldering skeletons.

And of course, just in case you not do this already, let the values of ALL monsters vary so that you might never know for sure if you face a weakling, an average or a champion version of the enemy. I ever hated when gamers could quote every value of a monster from the book for every single stat. I liked their faces when they laid bleeding on the ground before they realized they were not fighting enemies out of a clone factory.

Ideals are like stars. We might never reach them. But we can set our course by them.