Can I perform Qaza-e-Umari namaz in place of Sunnat-e-Muwakkidah, for example: 4 rakah qaza of Zuhr salah instead of 4 rakat sunnat-e-muwakkidah salah, likewise for Fajr? I hope its fine if I replace sunnat-e-ghair muwakkidah with qaza-e-umari in Asar and Isha salah (skipping 2 rakah sunnah after 4 fardh).
بسم الله الرحمن الرحيم
(Fatwa: 663/606/M=6/1439)
(1, 2) It is also important to offer waqtiya sunnah muwakkidah; hence you should not miss sunnah muwakkidah and keep on offering qaza-e-umari as well. Yes, you may offer qaza-e-umari instead of sunnah ghair muwakkidah.
Allah knows Best!
Darul Ifta,
Darul Uloom Deoband