Ibrad is delaying Dhuhr within its valid time until the severe heat has eased; it is not permission to carry Dhuhr into Asr.
أَبْرِدُوا بِالظُّهْرِ، فَإِنَّ شِدَّةَ الْحَرِّ مِنْ فَيْحِ جَهَنَّمَ
Translation: Delay Dhuhr until it cools, for intense heat is from the heat of Hell.
In winter, performing Dhuhr earlier is preferred. In both cases Dhuhr still begins only after zawal.