Seems to me Christians and Jews do worship one and the same God.
Judaism is monotheistic, they only believe in Jehovah. Christianity is trinitarian giving full divinity to the three Persons of the Godhead, Father, Son & Holy Spirit. Christ said that He is the only way to the Father, that there is NONE other. So while it is true that Judaism worships Jehovah, the Jehovah that they worship is not fully the Jehovah of Christianity.