sheep in a tiger's skin; all show and no substance
A yojijukugo describing someone or something that appears impressive outwardly but lacks real worth or substance. Used in literary or formal contexts.
His proposal was all show and no substance; it looked good but had no real value.
Leadership that is all show and no substance won't sustain an organization for long.
見かけ倒し is a more common, everyday expression for something that looks good but is disappointing in reality, while 羊質虎皮 is a formal, literary yojijukugo with the same meaning.
From Chinese 羊質虎皮 (yáng zhì hǔ pí), literally 'sheep quality, tiger skin', meaning outwardly fierce but inwardly weak. The exact historical derivation is uncertain; the spelling is conventionally associated with this meaning.