The generator matrix

 1  0  1  1  1  X  1  1  1  1  0  X  1  1  1  1  X  X  0  0  X
 0  1 X+1  X  1  1  0  X X+1  1  1  1  0  X X+1  1  0  X  X  1  1

generates a code of length 21 over Z2[X]/(X^2) who´s minimum homogenous weight is 22.

Homogenous weight enumerator: w(x)=1x^0+12x^22+3x^24

The gray image is a linear code over GF(2) with n=42, k=4 and d=22.
As d=22 is an upper bound for linear (42,4,2)-codes, this code is optimal over Z2[X]/(X^2) for dimension 4.
This code was found by Heurico 1.16 in 0.00101 seconds.