Is it prescribed to repeat the opening supplication (Du'a al-Istiftah) in the last two rak'ahs of a four-rak'ah prayer before Dhuhr, or should one proceed directly to reciting Al-Fatihah?

The opening supplication (Du'a al-Istiftah) is among the Sunnah acts of prayer, and it is prescribed for the worshiper to recite it after the Takbirat al-Ihram (the opening Allahu Akbar). If the prayers are four rak'ahs before Dhuhr and are performed with two taslims (salam at the end of prayer), the opening supplication is recited in both prayers after the Takbirat al-Ihram. However, if the four rak'ahs are performed with a single taslim, then the opening supplication is recited only once after the Takbirat al-Ihram. The opening supplication is recited in the first rak'ah of every obligatory or vowed prayer, and in the first rak'ah of a regular supererogatory prayer (like the rawatib of Fajr and Dhuhr), as well as in the first two rak'ahs of voluntary prayers like Tarawih and Duha.