There are a multitude of differences between Genesis chapter 1 and Hesiod’s Theogony.
One immense difference between Genesis 1 and the Theogony is that in Genesis the world was created very peacefully and easily while in the Theogony chaos was the main root of everything existing.
Another huge difference is that in Genesis and the whole Bible there is only one God, an omnipotent- all powerful, omnipresent-everywhere at once, and omniscient-all knowing, God who made all things. In contrast there are many varying gods in the Theogony– gods who are not omnipotent, omnipresent, and omniscient and numerous gods “made” all things.
The elements in the two passages also have their differences. The elements in the Theogony are made of quarrelsome gods who are known to make trouble for mankind whereas the Biblical elements are just plain, pure, and simple elements, existing on earth for the benefit of man.
To sum it all up there are many irregular differences between Genesis 1 and the Theogony that show us how inconsistent some things in this world can be- especially ancient Greek literature.