What is the ruling on the prayer of one who prays from beginning to end, says the opening takbeer (takbeerat al-ihram) with the imam, then recites Al-Fatiha and what is easy from the Qur'an by himself in a low voice, and delays behind the imam in bowing (ruku') and prostrating (sujud)?

It is disliked for the worshipper (ma'mum) to coincide with the Imam in the opening Takbir (Takbirat al-Ihram). According to the majority of jurists, the prayer of the worshipper becomes invalid if he intentionally or forgetfully coincides with the Imam in it. The Shafi'is and Hanbalis hold that the worshipper's Takbir must be after the Imam's Takbir, while Abu Hanifa sees no harm in coinciding with it. If "to say Takbir with the Imam" refers to preceding him in recitation or the like, then the prayer is not invalidated by that.