Online Etymology Dictionary

zoolatry (n.): "worship of animals or an animal," 1817, from zoo- + -latry. Related: Zoolater; zoolatrous.
zoological (adj.): 1807, from zoology + -ical.
zoologist (n.): 1660s, from zoology + -ist.
zoology (n.): "science of animals," 1660s, from Modern Latin zoologia, from Greek zoion "animal" (see zoo-) + -logia "study" (see -logy).
zoom (v.): 1886, of echoic origin. Gained popularity c. 1917 as aviators began to use it. As a noun from 1917. The photographer's zoom lens is from 1936, from the specific aviation sense of zoom as "to quickly move closer."
zoomorphic (adj.): "representative of animals," especially representative of a god in the form of an animal, 1872, from zoo- + morphe "shape" (see Morpheus) + -ic. Related: Zoomorphism.
zoon (n.): "animal form containing all elements of a typical organism of its group," 1864, from Greek zoion "animal" (see zoo-).
zoonosis (n.): "disease communicated to humans by animals," plural zoonoses, 1876, from zoo- "animal" + nosos "disease" (see noso-).
zoonotic (adj.): 1900, from zoonosis + -ic.
zoophagous (adj.): "carnivorous," 1840, from zoo- + -phagous. Related: Zoophagy; zoophage.
zoophilia (n.): "attraction to animals involving release of sexual energy," 1899, in a translation of Krafft-Ebing, from zoo- "animal" + -philia. "[F]ormerly not implying sexual intercourse or bestiality" [OED]. The meaning "sympathy or tender care for living creatures" is in the nativized formation zoophily (1886).
zoophobia (n.): 1901, from zoo- "animal" + -phobia. Related: Zoophobic; zoophobe.
zooplankton (n.): 1901, from zoo- "animal" + plankton.
zoot suit (n.): 1942, American English slang, the first element probably a nonsense reduplication of suit (compare reet pleat, drape shape from the same jargon).
zooxanthella (n.): plural zooxanthellae, yellow pigmentary particles found in nature, 1889, from German (Brandt, 1881), from comb. form of Greek zoion "animal" (see zoo-) + xantho- "yellow" (see xantho-) + Latin suffix -ella.
zori (n.): 1823, from Japanese zori, from so "grass, (rice) straw" + ri "footwear, sole."
Zoroastrian (adj.): 1743, from Zoroaster, from Latin Zoroastres, from Old Persian Zarathushtra, 6c. or 7c. B.C.E. Persian religious teacher. The name appears to be literally "whose camels are old," from *zarant "old" (cognate with Greek geron, genitive gerontos "old;" see gerontology) + ushtra "camel." As a noun from 1811.
Zoroastrianism (n.): 1854, from Zoroastrian + -ism.
zorro (n.): 1838, "South American fox-wolf," from Spanish zorro, masc. of zorra "fox," from Basque azaria "fox." The comic book hero, a variation on the Robin Hood theme set in old Spanish California, was created 1919 by U.S. writer Johnston McCulley (1883-1958).
zoster (n.): kind of seaweed, c. 1600, Latin, from Greek zoster "girdle," originally "warrior's belt," from zonnynai (see zone (n.)). Meaning "shingles" is from 1706; in the literal sense, "a belt or girdle, especially for men," from 1824.
zouave (n.): member of a French light infantry troop, 1848, from French, from Arabic Zwawa, from Berber Igawawaen, name of a Kabyle tribe in Algeria, from which the zouaves originally were recruited in 1831. The military units soon became exclusively French but served only in Algeria until 1854 and were "distinguished for their dash, intrepidity, and hardihood, and for their peculiar drill and showy Oriental uniform" [Century Dictionary]. Some Northern regiments in the American Civil War adopted the name and elements of the uniform. The women's fashionable zouave jacket (1859) also is based on the uniform.
zouk (n.): Creole French, "party," from zouker "engage in unrestrained social activity."
zounds (interj.): c. 1600, oath of surprise or anger, altered from (by) God's wounds!, in reference to the wounds of Christ on the Cross. "One of the innumerable oaths having reference to Christ's passion" [Century Dictionary]. Compare gadzooks.
zowie (interj.): expression of astonishment, c. 1913.
zucchetto (n.): small, round skull-cap worn by dignitaries in the Catholic Church, 1853, from Italian zucchetta "a cap," originally diminutive of zucca "gourd, head," perhaps from Late Latin cucutia, of unknown origin.
zucchini (n.): 1915 in English cookery books, 1910 in travel books about Italy as an Italian word (defined as "an odd kind of little squash, very tender and palatable"), from Italian, plural of zucchino, diminutive of zucca "gourd, squash," perhaps from Late Latin cucutia, which is of unknown origin.
zugzwang (n.): 1904, in chess, from German Zugzwang, literally "move-compulsion," from Zug "move (in chess), a drawing, pulling, a stretch," from Old High German ziohan "to pull," from Proto-Germanic *teuhan, from PIE root *deuk- "to lead" (see duke (n.)).
Zulu (n.): one of a Bantu people of South Africa, 1824, a native name. As radio code word for -z- from 1960.
Zuni (n.): native people and language of New Mexico, 1834, from Spanish, from a local native word.
Zurich: city and lake in Switzerland, German Zürich, said to be ultimately from Celtic root *dur- "water."
zwieback (n.): 1894, from German Zweiback "biscuit," literally "twice-baked," from zwei "two, twice" + backen "to bake;" loan-translation of Italian biscotto (see biscuit).
Zwinglian (adj.): 1532, after Ulrich Zwingli (1484-1531), Swiss Protestant reformer who revolted from the Roman communion in 1516 but who differed from Luther on theological points relating to the real presence in the Eucharist.
zydeco (n.): 1949, perhaps from Creole French pronunciation of French les haricots "the beans," part of the title of a popular dance tune ("les haricots sont pas salés").
zygoma (n.): "bony arch of the cheek," plural zygomata, 1680s, Modern Latin, from Greek zygoma, from zygon "yoke" (see jugular). So called because it connects the bones of the face with those of the skull about the ear.
zygomatic (adj.): "pertaining to the zygoma," 1709, from Latin zygomaticus, from Greek zygoma (see zygoma).
zygote (n.): 1880, coined 1878 by German cytologist Eduard Strasburger (1844-1912), the widespread attribution to William Bateson being apparently erroneous; from Greek zygotos "yoked," from zygon "yoke" (see jugular).
Zyklon (n.): type of fumigant used to kill rats in enclosed spaces, such as holds of ships, boxcars, etc., 1926, from German Zyklon, commercial name of a type of hydrogen cyanide, said to be of unknown etymology, but it is the usual German form of the word cyclone. There were at least three varieties, A, B, and C, Zyklon-B being the one notoriously used in the Nazi death camps.
zymurgy (n.): branch of chemistry which deals with wine-making and brewing, 1868, from Greek zymo-, comb. form of zyme "a leaven" (from PIE root *yeue-; see juice) + -ourgia "a working," from ergon "work" (see organ).

The last word in many standard English dictionaries (and this one); but Century Dictionary ends with Zyxomma ("A genus of Indian dragon-flies") and in the OED [2nd ed.] the last word is zyxt, an obsolete Kentish form of the second person singular of see (v.).
At the dictionary's letter A
Mr. Brandt is young and gay
But when at last he reaches zed
He's in his wheelchair, nearly dead

[Einar Haugen]