The Collaborative International Dictionary of English v.0.48:

zestful \zest"ful\ (z[e^]st"f[.u]l), adj.
   Marked by spirited enjoyment.

   Syn: yeasty, zesty.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

zestful
    adj 1: marked by spirited enjoyment [syn: zestful, yeasty,
           zesty, barmy]

Moby Thesaurus II by Grady Ward, 1.0:

103 Moby Thesaurus words for "zestful":
   active, acute, aggressive, agog, alacritous, all agog, animated,
   antic, anxious, avid, bracing, breathless, brisk, burning,
   bursting to, capersome, cheering, coltish, cordial, crisp, crispy,
   curried, desirous, dynamic, eager, energetic, energizing,
   enterprising, enthusiastic, exhilarating, exuberant, forceful,
   forcible, forward, fresh, frisky, frolicsome, full of beans,
   full of life, full of pep, gamesome, gay, go-go, hearty,
   high-seasoned, hot, hot as pepper, impatient, impetuous, incisive,
   intense, invigorating, keen, kinetic, lively, living, lusty,
   mettlesome, nippy, panting, peppery, peppy, playful, prompt, quick,
   racy, raring to, ready, ready and willing, refreshful, refreshing,
   regaling, robust, rollicking, rollicksome, rompish, rousing,
   seasoned, skittish, smacking, snappy, spanking, spiced, spicy,
   spirited, sportive, sprightly, stimulating, strenuous, strong,
   take-charge, take-over, tangy, tonic, trenchant, vibrant, vigorous,
   vital, vivacious, vivid, with a kick, zesty, zippy