Flattening multilevel list formats

Questions
1

{{{{36 - 72 m^2}, {-36}, {9 + 8 m^2}}, {{4 - 2 e m - 9 m^2 +
3 d m^2}, {-4 + e m + d m^2}, {1 + m^2}}}, {{{-40, 32 m,
9 + 8 m^2}}, {{-5 + 5 d, e + 4 m + d m, 1 + m^2}}}}

How to convert the above output into the format shown below?

{{{36 - 72 m^2, -36, 
   9 + 8 m^2}, {4 - 2 e m - 9 m^2 + 3 d m^2, -4 + e m + d m^2, 
   1 + m^2}}, {{-40, 32 m, 9 + 8 m^2}, {-5 + 5 d, e + 4 m + d m, 
   1 + m^2}}}

My current implementation seems suboptimal in terms of conciseness. Could you suggest more efficient methods?

original = {{{{36 - 72 m^2}, {-36}, {9 + 8 m^2}}, {{4 - 2 e m - 
       9 m^2 + 3 d m^2}, {-4 + e m + d m^2}, {1 + m^2}}}, {{{-40, 
      32 m, 9 + 8 m^2}}, {{-5 + 5 d, e + 4 m + d m, 1 + m^2}}}};
firstLayer = Flatten /@ original[[1]];
secondLayer = Flatten /@ original[[2]];
result = {firstLayer, secondLayer}
2

This flattens levels 3 and 4:

Flatten[original, {{1}, {2}, {3, 4}}]
3
Open in Wolfram Cloud ↗
4

This method is great, thank you very much!

5

Great method, it utilizes level operations—thank you very much!

6

original = {{{{36 - 72 m^2}, {-36}, {9 + 8 m^2}}, {{4 - 2 e m -
9 m^2 + 3 d m^2}, {-4 + e m + d m^2}, {1 + m^2}}}, {{{-40,
32 m, 9 + 8 m^2}}, {{-5 + 5 d, e + 4 m + d m, 1 + m^2}}}};
Map[Flatten, original, {2}]