1. Zayd bin 'Ali ash-Shahid:
Among the children of Imam 'Ali Zaynul 'Abidin (a.s.), after Muhammad al-Baqir, Zayd was the most outstanding and the most learned. Shaykh Mufid describes him as "a devout worshipper, pious, a jurist, God-fearing and brave." (al-Irshad, p. 403) It is worth mentioning that he is also the first narrator of the famous as-Sahifah as-Sajjădiyya of Imam Zaynul 'Abidin (a.s.).
Zayd led an armed rebellion against the Marwanid (the Umayyid clan which came to power after Yazid) ruler, Hisham bin 'Abdul Malik; and was calling people towards "the accepted person from among the descendants of the Prophet". He led the uprising in Kufa but was killed on 2nd Safar in 120 A.H. at the age of forty-two by Yusuf bin 'Amr ath-Thaqafi (the Umayyid governor), his body was taken out of the grave, put on a cross for four years, then it was burnt and his ashes were spread in the wind. (See al-Mufid, al-Irshad, p. 404; al-Mas'udi, Muruj adh-Dhahab; al-Qummi, Muntahal Amăl, p. 36).
Because of his jihad and his claim for the Ahlul Bayt, some Shi'as, however, thought that Zayd was claiming imamate for himself and therefore started believing in him as the Imam.
The Ithna-'Ashari sources do not believe that Zayd claimed imamate for himself. For example, Shaykh Mufid, one of the earliest Shi'a theologians says, "However that was not his intention because he knew of the right of his brother, peace be on him, to the Imamate before him, and of his bequest of trusteeship (wasiyya) at his death to Abu 'Abd Allăh (i.e., Ja'far as-Sadiq), peace be on him." (al-Irshad, p. 404).
Even the way Imam Ja'far as-Sadiq (a.s.) reacted to Zayd's martyrdom shows the uprightness of the latter in his faith in the Imams of Ahlul Bayt. When Imam as-Sadiq was informed about Zayd's martyrdom, "he was very sad...and he set apart a thousand dinars of his own money for the families of those of (Zayd's) followers who were killed with him." (al-Irshad, p. 405) For other such narrations by Shaykh as-Saduq, see Muntahal Amăl, p. 36.
In conclusion, we can say that Zayd bin 'Ali was an outstanding Shi'a, a mujăhid and a shahid who was loyal to the line of the Imams of Ahlul Bayt, including his own brother, Muhammad al-Baqir, and, his nephew, Ja'far as-Sadiq (a.s.). This leaves us with no choice but to reject the statement made by the late 'Allamah Tabătabă'i that Zayd himself "considered the first two caliphs, Abu Bakr and Umar, as their Imams." (Shi'a Islam, p. 77)
2. The Zaydiyya Sect:
Among the three sub-sects of the Zaydiyya, al-Jărudiyya is extinct. The other two sub-sects, the Sulaymăniyya and the Batariyya, cannot be technically considered as "Shi'a". Both believe that the Prophet did not appoint anyone as his successor; both believe in the caliphate of Abu Bakr and 'Umar but not in the caliphate of 'Uthman; they do not believe in the infallibility of the Imams; they believe that it is possible to have two imams at the same time but in two different regions.
According to the Zaydiyya, any descendant of the Prophet (i.e., a sayyid) who is a jurist (faqih, mujtahid), pious, courageous, and calls people towards Allăh by the "sword" (i.e., jihad) can be the imam. (On this account, the late Ayatullah al-Khumayni was definitely fulfilling all these requirements for the imamate of the Zaydis! I wonder what the Yemeni Zaydis have to say about this? But, on the other hand, they might say that this would apply to the Zaydis in Iran only!!)
All historians of religion, Shi'ahs and Sunnis, say that the Zaydis follow the Mu'tazila school in their beliefs, and the Hanafi school in their laws. As such, the Zaydis are more closer to the Sunnis than the Shi'as. (For details, see S.S. Akhtar Rizvi, "Shi'a Sects" published in The Light, and also reprinted in The Right Path [Toronto] in 1995).
3. Zaydi States:
It is true that one of the earliest states founded by the descendants of Imam 'Ali (a.s.) was a Zaydi state, but it was not necessarily a Shi'a state for the reasons mentioned above. Năsir al-Utrush, a descendant of the brother of Zayd ash-Shahid, arose in Khurasan. After being pursued by the 'Abbasids, he fled to Mazandaran (Tabaristan) whose people had not yet accepted Islam. "
After thirteen years of missionary activity in that region he brought a large number of people into the Zaydi branch of Islam. Then in the year 301/913 with their aid he conquered the region of Mazandaran, becoming himself Imam." (Tabătabă'i, Shi'a Islam, p. 77) The Zaydi rule in Tabaristan continued until 1126 C.E.
The Idrisi dynasty (from 788-985 C.E.) in Morocco was not a Zaydi dynasty. It was founded by Idris bin 'Abdullah, a great-grandson of Imam Hasan bin 'Ali (a.s.).
4. What is our response?
Since the Zaydiyya believe in the caliphate of Abu Bakr and 'Umar, our response and arguments with them should not be any different from our arguments for the Sunnis.