集中 (jízhōng) can be a verb ('to concentrate, centralize') or an adjective ('concentrated, centralized'). It applies both to mental focus (e.g., 集中注意力) and to physical/organizational centralization. In contrast, 专心 (zhuānxīn) and 专注 (zhuānzhù) are adjectives meaning 'attentive, absorbed', used only for attention — they don't carry the idea of gathering or centralizing things.