Here is an important part of the Gospel which Paul reveals in Galatians 3:
"He therefore that ministereth to you the Spirit, and worketh miracles among you, doeth he it by the works of the law, or by the hearing of faith?
6. Even as Abraham believed God, and it was accounted to him for righteousness.
7. Know ye therefore that they which are of faith, the same are the children of Abraham.
8. And the scripture, foreseeing that God would justify the heathen through faith, preached before the gospel unto Abraham, saying, In thee shall all nations be blessed.
9. So then they which be of faith are blessed with faithful Abraham." Galatians 3: 5-9
"Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.
17. And this I say, that the covenant, that was confirmed before of God in Christ, the law, which was four hundred and thirty years after, cannot disannul, that it should make the promise of none effect." Galatians 3: 16-17
"For ye are all the children of God by faith in Christ Jesus.
27. For as many of you as have been baptized into Christ have put on Christ.
28. There is neither Jew nor Greek, there is neither bond nor free, there is neither male nor female: for ye are all one in Christ Jesus.
29.And if ye be Christ's, then are ye Abraham's seed, and heirs according to the promise." Galatians 3: 26-29
Here Paul reveals the mystery that those who are the elect of God are no longer defined physically, by their DNA from Abraham. In Genesis 17:11 God demands obedience to be literally and physically circumcised. "Genesis 17:11 says "And you shall be circumcised in the flesh of your foreskin, and it shall be the sign of the covenant between Me and you."
But God says in Deuteronomy 10:16, "Circumcise therefore the foreskin of your heart, and be no more stiffnecked." This is a change from Genesis 17: 11, demanding obedience to a literal and physical circumcision to obedience to a metaphoric circumcision - he is not talking about literally cutting part of your heart off. He is talking about something else, a change of heart toward him and toward his doctrines.
Then in Galatians 3: 5-9 God, through Paul, makes a bigger change, shifting from obedience to circumcision - literal or metaphoric - to the working of the Holy Spirit through faith.
Then God, by Paul, goes farther and says that the faith of Abraham was accounted to Abraham as righteousness by God. Abraham becomes righteous before God by his faith. Obedience is being shifted toward faith or belief, an internal change in Abraham like that transformation in Romans 12: 2. "In thee (Abraham) shall all nations (peoples) be blessed - so they which be of faith are blessed with faithful Abraham." Abraham becomes the model of faith; so that it is now Abraham's faith which is given through the sacrifice of Christ to those who accept Christ and his sacrifice.
In his faith Abraham becomes the faith son of Abraham, while before Abraham was the physical, literal father of Christ in that bloodline. But Christ changed the physical bloodline to spiritual faith, which is the foundation of the Gospel.
There are Old Testament texts other than Deuteronomy 10: 16 which talk about obedience to the circumcision of the heart, which is not literal but metaphoric, or spiritual. Remember than C. I. Scofield says that no prophecy can be spiritualized??
"And that I also have walked contrary unto them, and have brought them into the land of their enemies; if then their uncircumcised hearts be humbled, and they then accept of the punishment of their iniquity:" Leviticus 26: 41
"Circumcise yourselves to the LORD, and take away the foreskins of your heart, ye men of Judah and inhabitants of Jerusalem: lest my fury come forth like fire, and burn that none can quench it, because of the evil of your doings." Jeremiah 4: 4 Again, God is asking for obedience, but not something literal and physical, but a spiritual change of heart.
What exactly are the Christian Zionist's arguing against in this thread? Are they just arguing against whatever is the Truth, whatever is absolute? Yes, but they may be also be arguing against that change from obedience to faith that Paul reveals to be at the heart of the Gospel of Christ in Galatians 3
There is a spiritual growth in the change from obedience to faith, which does not do away with obedience but in surpassing obedience it retains it in faith.