The generator matrix

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

generates a code of length 21 over Z4[X]/(X^2+2) who´s minimum homogenous weight is 15.

Homogenous weight enumerator: w(x)=1x^0+104x^15+879x^16+3250x^17+11030x^18+28710x^19+52316x^20+68926x^21+53212x^22+28942x^23+10700x^24+2990x^25+846x^26+194x^27+40x^28+2x^29+2x^31

The gray image is a code over GF(2) with n=168, k=18 and d=60.
This code was found by Heurico 1.16 in 117 seconds.