chimera

A thing that is hoped or wished for but is in fact illusory or impossible to achieve; (mythology) a fire-breathing monster with a lion's head, goat's body, and serpent's tail.

• chimerical/kaɪˈmɛrɪkəl/(adj)幻想的

• mere chimera
• pursue a chimera
• chimerical dream
• ideological chimera

1. 1.The promise of a risk-free investment is nothing but a chimera. (impossible fantasy)
2. 2.Achieving perfect work-life balance may be a chimera, but the pursuit itself has value. (unattainable ideal)

• illusion/ɪˈluːʒən/— false belief
• fantasy/ˈfæntəsi/— unrealistic dream
• pipe dream /ˈpaɪp driːm/ (unattainable hope, informal)

from Greek "khimaira" = she-goat, then the mythological monster — an impossible hybrid, hence any impossible fantasy