Synonyms for Zealous:

adj.

active (adjective)
lively.
aggressive (adjective)
strenuous.
all (adjective)
avid.
energetic (adjective)
active, spunky, driven, vivacious, puissant, ardent, fervid, zippy, potent, forceful, powerful, mighty, snappy, vigorous, energetic, strong, effervescent, peppy, mettlesome, spirited.
enthusiastic (adjective)
afire, impassioned, enthusiastic, passionate, spirited, avid, excited, eager, earnest, dedicated, devoted, fervid, ardent, hooked, rabid, fervent, fanatical, warm, born-again, mad about something, wholehearted, motivated, burning.
extreme (adjective)
stern.
hardworking (adjective)
industrious.
lively (adjective)
animated.
overenthusiastic (adjective)
fanatical.
resolute (adjective)
loyal, dogged, tenacious, determined, serious, bullheaded, committed, persistent, set, indomitable, relentless, devoted, constant, steely, intent, unwavering, willing, uncompromising, deliberate, unshakeable, persevering, iron-willed, headstrong, ruthless, tough, earnest, decided, reliable, stern, resolute, bold, plucky, hearty, staunch, tireless, unflinching, steadfast, strong-willed, valiant, unchangeable, firm, dedicated, decisive, thorough, true, steady, resolved, implacable, unyielding, diligent, strong-minded, unbending, insistent, dauntless, inexorable, indefatigable, fearless, stubborn, faithful, spunky, courageous.
strong (adjective)
iron-willed.
vigorous (adjective)
fiery, lusty, full-blooded, potent, powerful, afire, ardent, mettlesome, puissant, vigorous, agitated, lively, passionate, frisky, virile, eager, enthusiastic, hearty, energetic, ablaze, emphatic, peppy, impassioned, strong, fervent, earnest, burning, industrious, active, zippy, excited, strenuous, zestful, spirited, prolific, animated, sprightly, exuberant.

n.

gung ho, crazy, warm, concern, rabid, mad, nuts. zealous (noun)
eager, great, enthusiastic, avid.

Other synonyms:

gung ho. warm. nuts, crazy. mad. fanatical
rabid.
Other relevant words:
hooked, crazy, avid, mad, great, rabid, warm, wholehearted, nuts.

Usage examples for zealous

  1. Nevertheless, he turned round rather sharply on Mr. Tookey, when the zealous deputy, feeling that this was a view of the case peculiarly suited to a parish- clerk, carried it still farther, and doubted whether it was right to inquire into a robbery at all when the circumstances were so mysterious. – Silas Marner The Weaver of Raveloe by George Eliot
  2. A zealous friend, let me add." – The Complete Project Gutenberg Works of George Meredith by George Meredith
  3. They always met with more generous relief from the private hands of the brothers themselves, and the remark, " that the ol' man was trying to set an example,- that he meant well,"- and that they would yet be thankful for his zealous care and economy. – Drift from Two Shores by Bret Harte