> collect(ass2,z2);
(-AB+BA)*z2

> collect(ass3,z3);
(ABB-2*BAB+BBA-AAB+2*ABA-BAA)*z3

> collect(ass4,z2);
(-2/5*ABBB+6/5*BABB-6/5*BBAB+2/5*BBBA+1/10*AABB-1/2*ABBA-1/2*BAAB+7/10*BABA
-1/10*BBAA-2/5*AAAB+6/5*AABA-6/5*ABAA+2/5*BAAA+3/10*ABAB)*z2^2

> collect(ass5,[z2,z3,z5]);
(AABBB-ABBBA-3*ABABB+2*BABAB+2*ABBAB+BABBA-BBAAB-2*BBABA+BBBAA-AAABB+ABBAA
+BAAAB-BAABA+2*BABAA-BBAAA-2*ABAAB-2*ABABA+3*AABAB)*z3*z2

+(ABBBB-4*BABBB+6*BBABB-4*BBBAB+BBBBA-2*AABBB+3*ABBBA+1/2*BAABB-9/2*BABBA
+1/2*BBAAB+11/2*BBABA-2*BBBAA+2*AAABB-1/2*AABBA-1/2*ABBAA-3*BAAAB+9/2*BAABA
-11/2*BABAA+2*BBAAA-AAAAB+4*AAABA-6*AABAA+4*ABAAA-BAAAA+11/2*ABABB-2*BABAB
-9/2*ABBAB+9/2*ABAAB+2*ABABA-11/2*AABAB)*z5

> collect(ass6,[z2,z3]);
(-8/35*ABBBBB+8/7*BABBBB-16/7*BBABBB+16/7*BBBABB-8/7*BBBBAB+8/35*BBBBBA
+6/35*AABBBB-2/5*ABBBBA-8/21*BAABBB+118/105*BABBBA-38/35*BBABBA-2/105*BBBAAB
+74/105*BBBABA-6/35*BBBBAA-23/70*AAABBB+11/21*AABBBA-89/210*ABBBAA+11/21*BAAABB
-13/70*BAABBA+17/42*BABBAA-89/210*BBAAAB+17/42*BBAABA-29/30*BBABAA+23/70*BBBAAA
+6/35*AAAABB-8/21*AAABBA-2/105*ABBAAA-2/5*BAAAAB+118/105*BAAABA-38/35*BAABAA
+74/105*BABAAA-6/35*BBAAAA-8/35*AAAAAB+8/7*AAAABA-16/7*AAABAA+16/7*AABAAA
-8/7*ABAAAA+8/35*BAAAAA-32/105*ABABBB+8/7*BABABB+2/35*BBABAB-4/35*ABBABB-6/5*BABBAB
+10/21*ABBBAB-53/105*ABAABB-37/42*ABABBA+143/210*BABAAB+31/70*BABABA+13/70*ABBAAB
+143/210*ABBABA+29/30*AABABB-37/42*BAABAB-53/105*AABBAB+10/21*ABAAAB-6/5*ABAABA
+2/35*ABABAA-4/35*AABAAB+8/7*AABABA-32/105*AAABAB-3/70*ABABAB)*z2^3

+(-1/2*AABBBB+1/2*ABBBBA+BAABBB-BABBBA+1/2*BBAABB+1/2*BBABBA-BBBAAB-BBBABA
+1/2*BBBBAA+AAABBB-3/2*AABBBA+1/2*ABBBAA-3/2*BAAABB+1/2*BABBAA+1/2*BBAAAB
+1/2*BBAABA+2*BBABAA-BBBAAA-1/2*AAAABB+AAABBA+1/2*AABBAA-ABBAAA+1/2*BAAAAB
-BAAABA+1/2*BAABAA-BABAAA+1/2*BBAAAA+ABABBB-4*BABABB+2*BBABAB+1/2*ABBABB
+2*BABBAB-ABBBAB+3/2*ABAABB+3*ABABBA-BABAAB-4*BABABA-ABBAAB-ABBABA-3*AABABB
+3*BAABAB+3/2*AABBAB-ABAAAB+2*ABAABA+2*ABABAA+1/2*AABAAB-4*AABABA+AAABAB)*z3^2