That doesn't answer how a married man and woman are "echad" like God is "echad".
And let's look into that. So this echad God of the Scriptures says "let US make man in OUR image, according to OUR likeness"
Divine purpose stated, the Divine act not described until 2:7, 21-24.
"Who is the image of the invisible God the Firstborn of every creature" Col. 1:15
"Who being the brightness of His glory and the express image of His person" Heb. 1:3
"These things saith the Amen, the faithful and true Witness the beginning of the Creation of God." Rev. 3:14
Refers to the likeness of the image of the outward form, just as He took human form in order to redeem, He thus by His express image creates, indication of the similtude of creation of man, His Divine purpose being for the physical likeness Fig.
Hendiadys. the image has become two, where by before only the first born - one. The likeness to elohim.