Yeah, that's a good point, because that is what Zakir Naik's fans love about him; the fact that he has memorised the Qur'an, the Bible, the Bhagavad Gita etc. But if you look at his arguments, either he is deliberately misleading people or he has poor analytical skills.
I don't think you need someone who has memorised these scriptures to defeat him. You just need someone who know his/her stuff, knows how to easily look it up and reveal the misleading claims of Naik in front his face an his audience.
My wife was looking at Peace Channel last week and he was on saying that 80% of all the science in the Qur'an has been proven correct. The remaining 20% has not yet been discovered by modern science so he will put is trust that the 20% unknown stuff like Jinns, Hell, Heaven is true.
It was so funny but the sad thing was the huge audience lapping it up cheering.