In 1Corinthians 8:6 there are two agencies expressed, ultimate and intermediate. The NT pattern is that the Father is the source and the Son is the instrument. As BDAG says for δια
Christ as intermediary in the creation of the world J 1:3, 10; 1 Cor 8:6; Col 1:16
In 1Co 8:6 and Hebrews 1:2, both agents are in view. In John 1:3 and Col 1:16 only the intermediate agent with passive verbs are expressed. But a cohesive hermeneutic will understand the Father is the ultimate agent.
When a subject is the one who performs the action of a verb, they are the ultimate agent. When God “created” with the Hebrew verb BARA in Genesis 1:1, that verb which expresses Creation Ex Nihilo, would correspond to the ultimate agent. That's not to say there was no intermediate agent (Ge 1:26).
Thus if there were a correspondence between Ge 1:1 and J 1:1, God in both places is the subject who is the ultimate agent.
Attempting to make God the intermediate agent in John 1:1 makes no logical sense except for a modalistic view where the Word is a property of God and not a person with God.
It's also an impossible view when one gets to John 1:10 where ο κόσμος is δια ο Λόγος. This is obviously a reference to John 1:3-4.
Note: Since John 1:10 "the world came into existence through him" (ὁ κόσμος δι’ αὐτοῦ ἐγένετο) is a restatement of "all things came into being through him" (πάντα δι αὐτου ἐγένετο) from John 1:3, and it uses the same language including the singular masculine pronoun, as 1:10 andwhere the pronoun has the Word as it's antecedent, this must also be the case at 1:3. End Note
So the pronouns must refer to the Word in John 1:3-4 just as it does in verse 10.