How long does the dhur prayer last for?

بسم الله والحمد لله والصلاة والسلام على رسول الله وعلى آله وأصحابه ومن والاه أما بعد In brief, the time for Thuhr according to the four accepted Sunni Fiqh schools are as follows: Maliki, Shafi'i and Hanbali: Thuhr begins when the sun passes the zenith (meaning when the sun has passed the highest part of the sky and started to descend towards the west) and ends when the shadow of an object becomes as long as its height + the length of the shadow of the object at the time of the zenith. So, let's say the height of an object is 1m and the length of the shadow at the time of the zenith is 0.05m, the time for Thuhr will end when the height of the shadow reaches 1.05m which is the sum of 1m+0.05m. Hanafi: Thuhr begins when the sun passes the zenith (meaning when the sun has passed the highest part of the sky and started to descend towards the west) and ends when the shadow of an object becomes twice as long as its height + the length of the shadow of the object at the time of the zenith. So, let's say the height of an object is 1m and the length of the shadow at the time of the zenith is 0.05, the time for Thuhr will end when the height of the shadow reaches 2.05m which is the sum of twice the height of the object + the length of the shadow of the object at the time of the zenith (1m)(2)+0.05m. Below are some references from the Mu'tamad works of each school: Hanafi: Al Nasafi mentions in his book Kanz Al Daqaa'iq p.151: والظّهر من الزّوال إلى بلوغ الظّلّ مثليه سوى الفيء "And Thuhr is from Zawal (i.e. when the sun passes the zenith (meaning when the sun has passed the highest part of the sky and started to descend towards the west)) until the shadow of an object becomes twice as long as its height excluding the length of the shadow of the object at the time of the zenith." Maliki Khalil mentions in his book Mukhtasar Khalil p.27: الْوَقْتُ الْمُخْتَارُ لِلظُّهْرِ: مِنْ زَوَالِ الشَّمْسِ لِآخِرِ القامة بغير ظل الزوال "The chosen time for Thuhr is from the Zawal of the sun till the end of Al Qaamah (referring to the shadow of an upright object becoming equal in length to the height of said object) excluding the length of the shadow of the object at the time of the zenith" Shafi'i Al Nawawi mentions in his book Minhaj Al Talibin p.21: وأول وقته زوال الشمس وآخره مصير ظل الشيء مثله سوى ظل استواء الشمس "And its beginning time is from the Zawal of the sun and its ending time is when the shadow of an object becomes as long as its height excluding the length of the shadow of the object at the time of the zenith." Hanbali Al Hajjawi mentions in his book Al Iqnaa' p.82: ووقتها من زوال الشمس: وهو ميلها عن وسط السماء...ويمتد وقت الظهر إلى أن يصير ظل كل شيء مثله بعد الذي زالت عليه الشمس إن كان "Its time is from the Zawal of the sun which is when the sun descends from the middle of the sky...and the time for Thuhr continues until the shadow of everything is equal to the length of said everything after considering the shadow present at the time of Zawal, if there is any" هذا وصل اللهم على محمد وعلى آله وصحبه وسلم