،السلام علیکم و رحمة الله و بركاته Being a Musaffir, is it Halal to lead a Jamma3 of Muqims in all 4 rakats of Dhuhr, not shortening his own prayer, or must he shorten his prayer? !بارك الله فيك وأكرمك أستاذ

It is allowed on the correct saying but u left out what is best which is that u pray 2 rakas and they can continue their salah, unless 1 of them is the imam, if this happens then you must pray 4 rakas even if u join the salah late.