But Zamenhof felt that the cause of human unity (he rarely used the word “universal”) was itself a Jewish cause; in fact, it was the mission to which God had dedicated the Jewish people. By 1901, he had named his cause Hilelismo, a choice that was at once naïve and revolutionary. He was naïve to think that a movement named for a first-century BCE Jewish rabbi would be received as anything but a Jewish affair. But Zamenhof needed Hillel in order to supersede, in one grand gesture, both Moses and Jesus. With Hillel, Zamenhof shifted the focus of Judaism from law to ethics, taking Hillel’s famous dictum – “Do not do unto others what is hateful to you” – as the epitome of Judaism. Like Felix Adler, founder of the Ethical Culture movement, he was trying to cast religion as a way of living ethically; like Mordechai Kaplan, the founder of Reconstructionism, he was trying to infuse Jewish spirituality with Haskalah ideals. At the same time, staking his vision on Hillel challenged the Christian monopoly on the “golden rule,” Jesus’s positive reformulation of Hillel’s dictum in his Sermon on the Mount (Matthew 7:12).
Under the pseudonym Homo Sum (“I am a man”), Zamenhof floated a “trial balloon” of Hillelism in 1901 in a Russian Jewish magazine. It did not get far: “I could not find a single person willing to help me in organizing such a sect as I contemplated.” Interviewed by The Jewish Chronicle in 1907, Zamenhof said that he’d intended to “call together a Jewish Congress and found a sect of Jews professing clearly defined philosophical principles.” The Russian Jewish Hillelists would preserve Jewish “customs and ceremonials, feasts and fasts; not, however, as laws, but as traditions.” Insofar as halacha was to be regarded not as binding laws but as cherished “folkways,” this was Reconstruction avant la lettre.
The bloody events of the revolutionary year 1905 renewed Zamenhof’s determination to press forward. Emboldened by the warm reception he had recently received at the First Esperanto Congress in Boulogne, he tried again, this time with an appeal to all Esperantists. In January 1906, a fictitious “Circle of Hillelists” issued The Dogmas of Hillelism, a twelve-point credo that reads like a cross between the “Rights of Man and the Citizen” and Maimonides’ “Ani Ma’amin.” Hillelists were entitled to their chosen or inherited religions, but vowed to reject any elements that failed to meet the severe ethical standards of Hillelism, such as nationalistic ideals; national, racial, and religious chauvinism; and doctrines offensive to one’s reason. In short, it was to be a sort of ethical quality control of religion. Hillelists would someday convene in Hillelist temples with Hillelist religious school and Hillelist programs for the elderly. And the language of Hillelism, of course, was to be Esperanto. The goal was a quiet, gradual transformation, “little by little, unremarked and without any disruption.”
Before the year was out, Zamenhof lightly revised the declaration, changing the movement’s name to Homaranismo (Humanitarianism). He was, in part, pandering to non-Jewish Esperantists, recasting a movement grounded in Jewish ethics as a “philosophically pure monotheism.” But Homaranismo required Zamenhof to come clean on what he meant by monotheism. God, he wrote in a richly ambiguous statement, was “a united ideal for all Humanity.” Zamenhof hoped that Esperanto would eventually unite humanity in a belief in God, but he was also suggesting that God was defined by the unity of human beings. Esperanto was to do the Jewish work of saving the world, soul by speaking soul.
From 'Esperanto - A Jewish Story', by Esther Schor
And here You have both booklets by Zamenhof