The following code does no compile with the error:
onlineapp.d(3): Error: cannot implicitly convert expression `0` of type `int` to `int[6][3]`

But for the simpler case of vector and if the matrix is in a function scope it works, just like the specification states https://dlang.org/spec/arrays.html#rectangular-arrays

```d
import std;

int[6][3] matrix = 0;
int[6] vector = 0;
void main()
{
    int[6][3] stackMatrix = 0;
}
```