eat like a horse 饭量惊人

straight from the horse’s mouth 十分可靠的消息

a horse of different color 一种完全不同的情况

Please get off your high horse.

不要这么骄傲自大。

To me, writing and spelling are easy. But math, that’s a horse of different color.

写作对我来说很简单，数学嘛，那就是完全不同的情况啦

Don’t put the cart before the horse.

耐心一点。