Can I pray the 4 nafl rakat after dhuhr without praying the 2 rakat before dhuhr?
This table of prayer rakat, from myislam.com explains which rakat are:
- Fardh (Farz) – These are mandatory or obligatory prayers. Missing is a sin on the believer.
- Sunnah Muakkadah – These are Mustahabb (highly encouraged) and the Prophet Muhammad (ﷺ) never missed them.
- Wajib – Is compulsory but not the same extent as fardh. Missing is a sin but not as severe as missing a fardh prayer.
- Nafl – optional, Prophet Muhammad (ﷺ) prayed these occasionally.
See What is the difference between fard and wajib? for an explanation of the difference between Fard and Wajib.
|Prayer||Sunnah (before Fard)||Fard||Sunnah (after Fard)||Nafl (before Wajib)||Wajib||Nafl (after Wajib)|
You can see that for Dhuhr, the prayer before the Fard is Sunnah Muakkadah and consists of 4 rakat, and the prayer after the fard is also Sunnah Muakkadah and consists of 2 rakat. The only nafl prayer for Dhuhr is after the 2 sunnah rakat.
That aside, I'm not aware of any ruling that says that preferring one Mustahaab act over another is forbidden or invalidates the other act. Also the following definition from wikipedia:
One definition [of Mustahaab] is "duties recommended, but not essential; fulfilment of which is rewarded, though they may be neglected without punishment".
— wikipedia article on Mustahaab
Implies neglecting one act is not punished, so there is no reason to think praying one and not the other sunnah prayer would make anything void or ignored.
And Allah knows best.