The generator matrix

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

generates a code of length 21 over Z4[X]/(X^2+2,2X) who´s minimum homogenous weight is 20.

Homogenous weight enumerator: w(x)=1x^0+6x^20+48x^21+6x^22+1x^24+1x^26+1x^34

The gray image is a code over GF(2) with n=84, k=6 and d=40.
This code was found by Heurico 1.16 in 0.00129 seconds.