How can a hindu boy marry a muslim girl with the consent of her parents?

Well if you are looking for Islamic law then its imposible for a girl to marry non-Muslims, but a Muslim can marry just jewish or christan girl from non-Muslims while for Muslims is forbidden to marry to Hindu girl...

What is the ruling of 15th of shaban?

In Islam, it is permitted to marry in a select few other religions. So long as they follow the same God, such as Christianity *of all kinds* and Judaism.

However it is not permitted at all to marry a polytheist. (one who believes in many gods) Hindu is polytheistic.

But besides that, even if Islam allowed it, In Hinduism it is not allowed at ALL to marry outside of Hinduism.

Here is the info you requested, the website for Dr. Zakir Naik.

https://www.askmehelpdesk.com/islam/questions-dr-zakir-naik-573046.html