All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
It is permissible for a wife to give the Zakaah of her money to her poor husband according to the most correct opinion of the scholars and this is also the opinion of the Shaafi'i school of jurisprudence and it is one of the two narrations of Imam Malik and Ahmad . The evidence about this is the Hadeeth in which Zaynab, the wife of ‘Abdullah Ibn Mas'ood said: “O Prophet of Allah! Today you ordered people to give alms and I had an ornament and I intended to give it as alms, but Ibn Mas'ood said that he and his children deserved it more than anybody else.” Thereupon, the Prophet said: “Ibn Mas'ood had spoken the truth. Your husband and your children had more right to it than anybody else”. [Al-Bukhari]
As regards the assistance of a wife to her husband –other than Zakaah – then it is a righteous act and it is permissible according to the agreement of the scholars as Allah Says (what means): {And give to the women (whom you marry) their dowry with a good heart, but if they, of their own good pleasure, remit any part of it to you, take it, and enjoy it without fear of any harm (as Allah has made it lawful).} [Quran 4:4]
This act is better than a wife giving Zakaah to her husband because of the difference of opinion among the scholars regarding the permissibility of a wife giving Zakaah to her husband as mentioned above.
Allah knows best.