Do Christians who worship Yahweh alone as God (as directed by Jesus) really worship Al-Lah? Yes.
Do Christians who worship Jesus as God really worship Al-lah? The answer is plainly no. My comments in *[ ...]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ from http://www.publishersweekly.com/978-0-06-192707-2 Allah: A Christian Response Miroslav Volf, HarperOne, $25.99 (336p) ISBN 978-0-06-192707-2
... is the God of the Qur'an the same as the God of the Bible? *[ Only Yahweh and not Jesus] ... the object of worship for both religions is the same (or at least the objects are "sufficiently similar"). *[ Incorrect. Many Christians worship Jesus as God. Jesus is a human and Al-Lah is not a human.] ... the comparison of the Christian Trinity to Allah. *[ Al-Lah like Yahweh is ONE God and not three gods.]
From the Koran 2:61 Believers, Jews, Christians, and Sabaens - whoever belives in Allah *[YAHWEH NOT JESUS] and the last day and does what is right - shall be rewarded by their Lord; they have nothing to fear.
For most Christians to worship Al-Lah one would have to prove that Jesus is really Al-Lah. Moselms would disagree as they do not view Jesus as God but as a prophet of Al-lah. Moslems do not believe in a trinity.
"Oh People of the Book! Commit no excesses in your religion, nor say of God anything but the truth. Christ Jesus, the son of Mary, was (no more than) a messenger of God, and His Word which He bestowed on Mary, and a spirit proceeding from Him. So believe in God and His messengers. Say not, 'Trinity.' Desist! It will be better for you, for God is One God, Glory be to Him! (Far exalted is He) above having a son. To Him belong all things in the heavens and on earth. And enough is God as a Disposer of affairs" (4:171).
"The Jews call 'Uzair a son of God, and the Christians call Christ the son of God. That is but a saying from their mouth; (in this) they but imitate what the unbelievers of old used to say. God's curse be on them; how they are deluded away from the Truth! They take their priests and their anchorites to be their lords in derogation of God, and (they take as their Lord) Christ the son of Mary. Yet they were commanded to worship but One God: there is no god but He. Praise and glory to Him! (Far is He) from having the partners they associate (with Him)" (9:30-31).
See video by Moslems at https://www.youtube.com/watch?v=9lTZR9X0Oow