WIST

Divide the work and thus you’ll shorten it.

[Divisum sic breve fiet opus.]

Martial (AD c.39-c.103) Spanish Roman poet, satirist, epigrammatist [Marcus Valerius Martialis]
Epigrams [Epigrammata], Book 4, Epigram 82
    (Source)

As quoted in Thomas Benfield Harbottle, Dictionary of Quotations (Classical) (1906); mislabeled as Epigram 83. Alt. trans.:

• "If it be too much to read two volumes, let them roll up one of them; and the task, thus divided, will seem shorter." [tr. Bohn (1871)]
• "If two be too much, double one parcel down; / So half, perhaps, better the pleasure will crown." [tr. Elphinston]
• "If it is too much to read two, let one book be rolled up: divided the work will thus become brief. [Si nimis est legisse duos, tibi charta plicetur / Altera: divisum sic breve fiet opus.]"  [tr. Ker (1919), Ep. 210]