Quran Teachings

The Quran's teachings are basically telling the followers or Islam what they should do and what they must be. The Quran also mentions how Allah should always be praised and how he should not be forgotten.  The relationship between Allah and human beings is that the humans follow him and he will reward them if they follow him with lots of devotion. 
Compared to Zoroastrians, Muslims must follow a set guideline, Zoroastrians followed moderation and did not have any "rules." Zoroastrians also followed other gods in addition to Ahura Mazda.  The Quran says "You alone we worship, and to You alone turn for help" which means they can only believe in Allah and no other gods.  When comparing Judaism, Christianity and Islam, the three say that they should only follow one God and one God only. 
Jews, Christians and Muslims all have something that tell them how they should behave and what they should be.  There are the Ten Commandments for Jews and Christians and the Five Pillars for Muslims.  The three also have some form of a judgement day just like Zoroastrianism. But the Quran and its teachings are very specific and strict compared to that of the other three religions. 

Bhagavad Gita: Compare and Contrast

The reflections on the caste duties and detachment are a combination of the on the moral and ethical teachings of Zarathrustra and Confucius.  Zarathrustra focused on moderation while Confucius focused on becoming a "junz" or a superior man.  The teachings in the Bhagavad Gita combine the two and state that a soul must have moderation so they do not get distracted and that they must fulfill their duty in the caste system.  

Zarathustra on Good and Evil Question

Zarathustra made assumptions that humans would make the bad choices as he is telling everyone that they should make the right choices.  Throughout the hymn, he refers back to doing good deeds and all the good choices that Ahura Mazda made while his twin made all the bad choices. There is a description of how the good followers would be rewarded and how the evil would have the worst experience. He also tells people that they have the choice to do whatever they desire. However, he emphasizes how the bad will suffer and how the good will not.  At then end, it says "Long punishment for the evil-doer, and bliss for the follower of Truth", which serves as a reminder that the follower of goodness won't be punished while the evil-doer will.  Overall, I think Zarathustra assumes that people will be more likely to make the bad choices and just need to be told that they need to be good.  After they are told to be good, they just need to be reminded to remain good and not fall towards the dark side.  The hymn really serves as a reminder for people that they should be morally good so they can be rewarded.