The phrase "cast envious eyes" refers to the act of looking at someone or something with jealousy or covetousness. If you're seeking synonyms for this phrase, you could consider using "look greedily," "regard covetously," "gaze enviously," or "view with envy." Other options might include "eye enviously," "peer jealously," or "observe covetingly." Ultimately, the synonym you choose will depend on the tone and context of your writing. However, by opting for a synonym for "cast envious eyes," you can add nuance and variety to your language and convey your meaning in new and interesting ways.