Praise be to Allaah.
You must mean, is the Sunnah prayer before Zuhr two rak’ahs or four rak’ahs? Because the one rak’ah is odd-numbered, and there is no odd-numbered prayer apart from Maghrib, and the Witr prayer at night.
The answer is: it was narrated in some ahaadeeth that the Sunnah prayer before Zuhr is with one tasleem (i.e., it is two rak’ahs), as stated in the hadeeth of Ibn ‘Umar (narrated) in al-Saheehayn.
And in some other ahaadeeth it is narrated that it is two tasleems (i.e., four rak’ahs), as stated in the hadeeth of ‘Aa’ishah (may Allaah be pleased with her), (narrated) in Saheeh Muslim.
So one has the choice of doing two or four rak’ahs. But some scholars suggested that if a person prays it at home it is better to pray four rak’ahs with two tasleems, and if he prays them in the mosque, he should pray two rak’ahs with one tasleem).