又要马儿跑得好，又要马儿不吃草yòu yào mǎ ér pǎo de hǎo , yòu yào mǎ ér bù chī cǎo

want the horse to run fast and yet unwilling to let it graze (/trying to save fodder); eat one’s cake and have it
❍ 你要母鸡多生蛋，又不给它吃米，～。世界上哪有这样的道理！ (《毛泽东选集》Ⅴ—274) You want the hen to lay more eggs and yet you don’t feed it,you want the horse to run fast and yet you don’t let it graze. What kind of logic is that!/天晓得，这批砂钢片，本来就是次货，铁耗怎么能不大？ 又要马儿好，又要马儿不吃草。(夏衍《考验》16)How the hell can iron wastage be low when that shipment of silicon steel is dud stuff in the first place!You can’t have your cake and eat it!