Nicomăchus in Harpers Dictionary of Classical Antiquities (1898)
A Greek painter, probably of Thebes, about B.C. 360. He was celebrated as an artist who could paint with equal rapidity and excellence, and was regarded as rivalling the best painters of his day. A famous painting of his was "The Rape of Persephoné" (Pliny , Pliny H. N. xxxv. 108).
Nicomachus of Thebes in Wikipedia
Nicomachus of Thebes (fl. 4th century BC) was an ancient Greek painter, a native of Thebes, and a contemporary of the great painters of the Classical period; his father and son were also painters. Vitruvius observes that if his fame was less than his contemporaries, it was the fault of fortune rather than a lack of talent.
Pliny gives a list of his works; among them a Rape of Persephone, Victory in a Quadriga, Apollo and Artemis, and Cybele seated on a Lion. Many of his works were taken to Rome. Pliny tells us that he was a very rapid worker and claims that he was one of the painters who used only four colors. Plutarch mentions his paintings as possessing the Homeric merit of ease and absence of effort.