Complex sentence: In 1923, while studying at the Vatican, Szekely translated several obscure Aramaic texts which, he claimed, proved that the Essenes were vegetarians, and that vegetarianism was prescribed by Jesus.
Split into simpler sentences: In 1923, Szekely claimed that while studying at the Vatican, he translated several obscure Aramaic texts. These texts, he claimed, proved that the Essenes were vegetarians, and that vegetarianism was prescribed by Jesus.