وَيُصَلِّي بِهِمُ الظُّهْرَ وَالْعَصْرَ فِي وَقْتِ الظُّهْرِ بِأَذَانٍ وَإِقَامَتَيْنِ.
Translation: He leads them in Dhuhr and Asr during Dhuhr time, with one adhan and two iqamahs.
This special combined congregational prayer uses one adhan, an iqamah for Dhuhr, and another iqamah for Asr. These remain two separate prayers.
The words fī waqt al-ẓuhr specify that Asr is performed here during Dhuhr time.