How is the letter "ḍād" (ض) correctly pronounced in the Holy Quran? Is it pronounced as a "dāl" (د) with a heavy emphasis, or as a "ẓāʾ" (ظ)?

The letter Dhad (ض) is articulated from the edge of the tongue and what adjoins it from the molars. It is characterized by the attributes of Jahr (voicing), Rakhawah (softness/laxity), Isti'la (elevation of the tongue), Itbaq (closure/adhesion of the tongue to the roof of the mouth), Istitalah (lengthening of the sound), and Ismat (inhibition/resistance). Tafashshi (spread of air) may also be added to its attributes. The letter Zha (ظ) shares all attributes with the Dhad (ض) except for Istitalah or Tafashshi. As for the letter Dal (د), it differs from Dhad (ض) in Rakhawah, Isti'la, Itbaq, Istitalah, and Tafashshi, agreeing with it only in Jahr and Ismat. Whoever is able to articulate the Dhad (ض) correctly is obligated to do so. For those who are unable, articulating it as a Zha (ظ) is closer and more preferable than articulating it as a glottalized Dal (د).