他想不花钱就把公司开起来,真是异想天开。Tā xiǎng bù huā qián jiù bǎ gōngsī kāi qǐlái, zhēnshi yìxiǎngtiānkāi.He wants to start a company without spending any money — that really is a fantasy.
别异想天开了,这种计划根本行不通。Bié yìxiǎngtiānkāi le, zhè zhǒng jìhuà gēnběn xíng bù tōng.Stop dreaming the impossible — a plan like this simply won't work.
这个主意听起来异想天开,但值得一试。Zhège zhǔyi tīng qǐlái yìxiǎngtiānkāi, dàn zhídé yī shì.This idea sounds wildly fanciful, but it's worth a try.