I can relate to the Christian understanding of Echad, even if I do not have their same viewpoint about expressing it. For you, focus on the part that states 'all one'. And how 'God' is the qualifier for each expression. For Christians, they see three (
all) as
one 'person'. Though I'm not a Christian that I would hold to the doctrine they way they do, I am a Jew who understands the oneness of God. To me the shema expresses this.
Hear Israel, the Lord our God, the Lord is One. We know and believe that Yeshua is Lord, and we know that Elohim is a compound unity. In a way you can understand the trinity by seeing the Lord as Yeshua and our God as the Father and the Spirit. So, when it says Adonai Eloheinu it states Yeshua our God, Yeshua is one. So when I read the shema I am confessing that Israel needs to hear the good news, Yeshua (is) our God, Yeshua is One (with the father and the spirit/Elohim). The Lord is our God. Yeshua is Lord, no? How can the Lord say to my Lord sit at my right hand?????
John 10:38
But if I am, then, even if you don’t trust me, trust the deeds; so that you may understand once and for all that the Father is
united with me, and I am
united with the Father.”
John 14:10-12 Complete Jewish Bible (CJB)
10 Don’t you believe that I am
united with the Father, and the Father
united with me? What I am telling you, I am not saying on my own initiative; the Father living in me is doing his own works. 11 Trust me, that I am
united with the Father, and the Father
united with me.
John 14:16-18 Complete Jewish Bible (CJB)
16 and I will ask the Father, and he will give you another comforting Counselor like me, the Spirit of Truth, to be with you forever. 17 The world cannot receive him, because it neither sees nor knows him. You know him, because he is staying with you and will be
united with you. 18 I will not leave you orphans — I am coming to you.
When Christians mention the trinity I'm usually reminded of what Paul said here;
2 Corinthians 3:16-18 New International Version (NIV)
16 But whenever anyone turns to the Lord, the veil is taken away. 17 Now
the Lord is the Spirit, and where the Spirit of the Lord is, there is freedom. 18 And we all, who with unveiled faces contemplate the Lord’s glory, are being transformed into his image with ever-increasing glory, which comes from
the Lord, who is the Spirit.