When he reached Muzdalifa, he prayed Maghrib and Isha there with a single adhan and two iqamas, and he did not perform any voluntary prayer between them. Then the Messenger of Allah ﷺ lay down to rest until dawn broke. The hadith continues.
حتى أتى المزدلفة، فصلى بها المغرب والعشاء بأذان واحد وإقامتين، ولم يسبح بينهما شيئا، ثم اضطجع رسول الله ﷺ حتى طلع الفجر… الحديث.
Muslim narrated it in the Hajj chapter (1218) via Hatim bin Ismail Madani, from Jafar bin Muhammad, from his father, from Jabir, mentioning the hadith of the Prophet's ﷺ Hajj in full. This is what Shafii said in his earlier position, and it is also a narration from Ahmad, and it is the choice of Tahawi by analogy with combining Dhuhr and Asr at Arafah. As for the later position of Shafii, it is as indicated by the coming hadith of Usama bin Zayd.This hadith of Jabir concerning the Prophet's ﷺ prayer at Muzdalifa is the primary reference, and whoever contradicts it is either shadh, in which case it should be disregarded, or sahih, in which case it needs to be interpreted so that the Prophet's ﷺ actions during his Hajj, which was not repeated, do not conflict with one another.As for what Zaylai mentioned in Nasb Raya (3/68), that Ibn Abu Shayba narrated it in his Musannaf with this same chain, and in it appears, "with one call to prayer and one call to stand," and he said, "This is a gharib hadith, for what is found in the long hadith of Jabir in Muslim is that he prayed the two prayers with one call to prayer and two calls to stand,"I say, this is what he said, but what is found in the printed editions of Hut (14050) and Lahham (4/347) is, "with one call to prayer and two calls to stand," matching the narration of Muslim. Perhaps this goes back to a difference among the manuscripts of the Musannaf. Allah knows best.