How is zakat on wealth given by working spouses? Does each of them give zakat on their wealth independently, or can their wealth be combined for zakat purposes? And is it permissible for the wife, who has independent control over her wealth, to choose the recipients of zakat herself, such as her needy relatives?

Mixing of wealth only affects livestock (Sā'imah). The view of the four Imams and others is that when two people mix their wealth in assets other than livestock, each of them must pay Zakat (definition) on their own wealth. If the wealth is mixed, then each of you is obligated to pay Zakat on what they own. If each of you has their own independent financial responsibility, then Zakat becomes obligatory on each person's wealth if it reaches the niṣāb (minimum threshold), and the two amounts of wealth are not combined to complete the niṣāb. Each of you has the option to disburse the Zakat to the recipient they choose. She has the right to give her Zakat to poor relatives, as this is more fitting for her, based on the Prophet's (peace be upon him) saying: "Charity given to the poor is charity, but charity given to a relative is two: charity and maintaining kinship ties."