Does performing prayers five or ten minutes before the Dhuhr athan prevent them from being valid?

It is prohibited to perform supererogatory prayers just before noon, at the time of the sun's meridian culmination—that is, when the sun casts no shadow. This period is estimated to be approximately ten minutes before Zawwal (the sun’s declination from its zenith). The wisdom behind this prohibition is that Hellfire is kindled during this time. This prohibition applies specifically to voluntary prayers and does not include obligatory prayers.