Why others religion more intelligent from muslims

To muslims,we must believe for the holy book which is consist of :

1. Injil ( bible )
2. Taurat (Old Testament)
3. Zabur
4. Quran

If we see the timeline, the quran is the last holy book from god via muhammad to human. The quran is a book contains all issues on what was stated in previous holy book and tell us about future.

The problem is, the muslims ourselves don't understand what was stated in quran. For the followers in bible, old testament and zabur they have long enough time to understand what were inside and they 100% believe in that holy book. That's why they can conquer the world.

And we are not doing research to other books. Major of us just sit and learn JUST ONLY to quran whereas there are 3 another holy book that god have deliver to mankind. If we can understand those 4 books...i think we are strong enough to live in peace in this world