I don't know why brother zakir is so worried. it's true that we Muslims are not good at advertisement and propaganda. even I can't speak in English. in my country, atheists became very active. unfortunately or fortunately, 2 of them were murdered.
well,those 2 were not true free thinkers.because a true free thinker stops talking after having the answer. but they didn't stop when Muslim bloggers answered . rather continued propaganda with other fake id and names, they used other blogs.
you can say,brother osama lost with him and him,because brother osama using his real name. but atheist bloggers open new blogs each time with fake names and each time they claim that he never lost to Muslim. and you can't call him liar as you don't know who is actually behind that blog.
however, if you search on Internet continuously, you will find at least one blog that answered your problem. answering Christianity may haven't answered all of them.
but Muslims have answered each objection here and there.