Please remember that our job is only to convey the Message, and not convincing people. About half a billion Hindus believe in the trinity of gods: Brahma, Vishnu and Shiva.
Can we make all mankind believe as we believe? No, Allah did not design that.
10:99 If your Lord willed, all who are on earth, would have believed. Would you then, compel people to become believers? [2:256, 76:4-6]
The Qur'an repeatedly cites the incredible discipline in the universe. Only One Creator and Sustainer could create and maintain that discipline.
When there are two or more wills, they must clash.
A tornado hitting a junk yard will not end up producing a Boeing 747. Even the "Big Bang" must have a Master Mind behind it.
- Islam As I Understand
The Universe is too organized to be the result of an accident.
In order to make an apple-pie from scratch, we would have to reinvent the Universe!
- Carl Sagan