The difference between God and Zeus is easily seen in various contexts.
The first of which is that God teaches us how to act; He reiterates upon values of discipline, courage, and loyalty to our values. God teaches us not to lie, not to harm others, and not to be greedy.
Jesus is the embodiment of such virtue. He is the archetypal perfect man: love thy neighbor, give to the poor, be honest, and much more.
Zeus is the complete opposite. Zeus is undisciplined, dishonest, and disloyal. Zeus is highly promiscuous and is without convictions.
The sons of Zeus (Hercules as one example) attack innocent people, are highly greedy, and are fueled by arrogance.
Additionally, one of the most significant differences between the two is the acceptance of repentance. Zeus is unforgiving which is seen by almost every measure; he tortured Prometheus, Tantalus, and ate his wife Metis.
In contrast, God tells us anyone can be saved through repentance.
John 15:12 is why God cannot be compared to Zeus. It is difficult to remain disciplined and loyal to your virtues, but in doing so you are rewarded - whether literal or metaphorical.