The generator matrix

 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1
 0  X  0  0  0  X  X 4X  0 3X  X 6X 3X  X 2X  0 4X 6X
 0  0  X  0  0 5X 4X 5X  X 4X 5X 5X 5X 2X 2X 3X 6X 6X
 0  0  0  X  0 5X 3X 3X 5X 5X  X 6X  0 3X 5X 6X 4X  0
 0  0  0  0  X 5X 6X  X 6X  X  X  0 3X 2X 2X 5X 2X  0

generates a code of length 18 over Z7[X]/(X^2) who´s minimum homogenous weight is 84.

Homogenous weight enumerator: w(x)=1x^0+630x^84+1446x^91+2100x^98+3708x^105+100842x^108+4692x^112+3282x^119+948x^126

The gray image is a linear code over GF(7) with n=126, k=6 and d=84.
This code was found by Heurico 1.16 in 2.75 seconds.