As the topic suggests, I burned my terrain in ZE. However it does not match anymore. How can I go about changing it back to the original?
I tried resaving the ground texture but it didn't work. I also manually cleaned, to no avail.

Burn it again. I think if there was a real reason to "unburn" it would be an option.

Burning it again didn't work. I also added a new layer of texture over the one I currently had. It didn't work, the terrain is still too dark.

Try opening the Color tab in ZE, select white, paint entire terrain.

The trick I use is to increase your lighting, burn, then set the lighting back to the original value.