What is the wisdom behind silent recitation of the Quran in the Dhuhr and Asr prayers, and audible recitation in the other prayers, and why is the Friday Dhuhr prayer only two audible rak'ahs?

Friday prayer consists of two rak'ahs by consensus (ijma'), as stated by Ibn al-Mundhir, and it has been reported in a tradition from Umar. It is said that its number of rak'ahs being two is a divinely ordained instruction (tawqif) that must be accepted in emulation of the Prophet, peace and blessings be upon him. The reason for this might be the presence of two sermons before it, which makes it suitable to shorten the prayer to two rak'ahs, similar to the situation in the Eid prayers, the prayer for rain (Istisqa'), and the eclipse prayer.