In the past I went through Shaykh Mufid's hadith books on the issue of Imamate on Imam Zayd (as), and he actually has ahadith on this topic which leans toward Nasabism.
Below is a reference from Shaykh Mufid Book Al Amali.
Abu Ghalib Ahmad b. Muhammad al-Zarari reported to me from Abul Qasim, Hamid b. Ziyad, who reported from al-Hasan b. Muhammad, who reported from Muhammad b. al-Hasan b. Ziyad al-Attar, from his father al-Hasan b. Ziyad who said:
When Zaid b. Ali advanced upon Kufa, some reservation entered my mind about it. He says: Then I went to Makkah, and passed by Madinah to call upon Abu Abdillah, peace be upon him, who was then ill. I found him lying prone on his bed, with nothing left between his skin and the bones. I said: "I wish to assert before you my creed." He turned on his side, and looking at me, said: "O Hasan, I always thought that you did not need this anymore." Then he said: "Proceed." So I said: "I testify that there is no god but Allah, and I testify that Muhammad is the messenger of Allah." He, peace be upon him, said: "The same with me, also." Then I said: "I confirm the truth of all that Muhammad b. Abdillah came with." He kept silent. Then I said: "And I testify that Ali is the Imam after the Prophet, and obedience to him is obligatory. Whoever doubts about him is gone astray, and whoever disputes his authority is an unbeliever." He kept silent. Then I said: "I testify that al-Hasan and al-Husain, peace be upon them, have the same position (as Ali)", and then I continued till I reached his name, and said: "And I testify that you are in the same position as al-Hasan and al-Husain and the Imams preceding you." He said: "Enough. You know exactly what you wish, you wish me to give my undertaking on this?" I said: "If you do so, then I will have fulfilled my desire." He said: "I give you my undertaking over it." I said: "May I be your ransom, I was worried about the uprising." He said: "Why?" I said: "Because if Zaid and his companions won the battle, then we would have been in the worst situation. And if Banu Umayya won, we would have been no better." He said: "Go, no harm will reach you from either." (Al Amali, Mufid)