Yahweh is one "He." Since Jesus is referring to HIS God, it is quite impossible for that one "HE" to be a Triune being. At Mark 12:28-34, Jesus the Jew & a Jewish scribe inform us the words of the Shema, "the LORD is one," do simply mean "there is no other but HE." The LORD is one HE. Jesus is speaking about HIS Yahweh, HIS God. HIS God was not a Triune Being. Jesus' God was his Father alone. Hence, that single "HE" for Jesus was his Father alone, "there is no other but He." The Shema, "the Lord is one" means there is no other but He, there is no other but Jesus' God, Jesus' Father.