He held professional positions in the Government, Municipal and Customs Laboratories, and made a number of applied and theoretical contributions.
He was awarded a canton of Zürich scholarship, which enabled him to continue his chemistry studies at the ETHZ and the University of Zurich along with other chemists Viktor Meyer and Georg Lunge.
In February 1887, the Education Council concluded that Alexander was sufficiently qualified to teach the natural sciences, especially chemistry and chemical technology, in which areas he had received a doctorate.
[5] In the meantime, he returned to Switzerland, where he got a job as an assistant in a chemical agricultural station, turning down an invitation to work at the high school in Pirot.
In 1894, Zega applied for the position of professor of chemistry and chemical technology at the Grandes écoles but Marko Leko was chosen instead.
He stayed in Ćuprija for a short time as a refugee, but returned to Belgrade at the beginning of 1916, where, with the permission of the occupiers, he managed to equip a chemical laboratory for testing food.
During the construction of the Belgrade water supply system, he spent days with experts and workers and helped with the correction of all chemical and technical deficiencies.
During his research, Zega strived to find methods to test foodstuffs that could be performed with simpler equipment while obtaining results that would meet strict European standards.
During the Austrian occupation of his county, in an improvised laboratory, he and his daughter developed a simpler method for determining the fat in milk, which excluded the use of a centrifuge.
The work is of a synthetic nature, and on that occasion, Zega obtained several aromatic amine compounds from p-toluidine with resorcinol or toluidine, from which he later found various derivatives.
[10] He was awarded the ribbon "For Honor and Loyalty", the "Dušan the Mighty" silver monument, and "The Best Knight" gold medal.
In 1921, at the celebration of the thirtieth anniversary of his work, he was awarded the Order of Saint Sava, 3rd degree by the Ministry of Education, Science and Technology Development.