بسم الله الرحمن الرحيم
You (daughters) may help your parents with gift, present and contribution. It is one of the methods of helping them. The second method is to read the following dua extensively for them:
رَّبِّ ارْحَمْهُمَا كَمَا رَبَّيَانِي صَغِيراً.
You (daughters) cannot give the amount of your zakah to your parents. However the zakah of your husbands could be given to your parents. Thus you should give the zakah of your husbands with their permission to your mother and father, Zakah will be paid. It is neither necessary to inform the husband to whom you are giving the zakah nor it is necessary to tell your parents what types of amount is given to them. You may also give them zakah money in the name of gift.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.