What is the ruling on obeying one's mother and ironing her dress or zipping up her tight dress that she wears in front of the questioner's adult brothers? Is that considered cooperation in sin and aggression?

If the mother's clothes conceal the 'awrah (parts of the body that must be covered) and do not incite فتنة (strife/temptation), then there is no harm in her wearing them in front of her adult sons. The daughter must obey and assist her. However, if the clothes are tight, accentuate the 'awrah, and incite فتنة, then it is not permissible for her to appear in them before her sons, nor is it permissible for the daughter to assist her. Rather, the daughter must advise her gently and politely, explaining the limits of a woman's 'awrah in front of maharim (unmarriageable kin), while being careful not to be harsh in speech or offensive. The duty to honor and treat the mother kindly remains in all circumstances.