The generator matrix

 1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  1  X  0  X  2  X 2X  X  1 2X+2  1  1  1  1  1  1  1  X  X  X  X  X  0  X  2  1  X 2X  1  X 2X+2  1  1  1  1  1  1 2X+2  X  X  X  X  0 2X+2 2X  X  X  X  X  0 2X  2 2X+2  1  1  1  1  1  1  1  1
 0  X  2 3X+2 2X X+2 2X+2 3X  0 3X+2  2 3X 2X X+2 2X+2  X  0 3X+2  2 3X 2X X+2 2X+2  X 3X+2  X 3X  X X+2  X  X  0  X 3X+2  2 3X 2X X+2 2X+2  X  0  2 2X 2X+2 3X+2  X 3X  X  0 X+2  X  2  X  X 2X 2X+2 3X+2 3X X+2  X  2  0  2 2X 2X+2 2X+2 2X+2 2X+2 3X+2 3X X+2  X  X  X  X  X  0 2X  2 2X+2  0 2X  0 2X

generates a code of length 84 over Z4[X]/(X^2+2X+2) who´s minimum homogenous weight is 84.

Homogenous weight enumerator: w(x)=1x^0+114x^84+9x^88+2x^92+1x^96+1x^104

The gray image is a code over GF(2) with n=672, k=7 and d=336.
This code was found by Heurico 1.16 in 0.39 seconds.