。
She shows no enthusiasm at all for her work.
Literal
She [topic-は] her own work [for-に] at-all enthusiasm [object-を] does-not-show.
ぜんぜん~ない ('not at all') is the standard pattern for total negation, where ぜんぜん combines with a negative predicate to deny something completely. The kana spelling ぜんぜん feels slightly more casual or softer than the kanji 全然. 熱意を示す ('to show enthusiasm') uses 示す ('to indicate, show, demonstrate') with an emotion or attitude as object — a clean Sino-Japanese collocation. に here marks the target of the (absent) enthusiasm.