Empresses in the Palace

Both femal leads refused to become a concubine in a large household.

Both were intelligent and careful but were cnstantly facing nasty tricks and plots.

An exact copy of the story.

Both FLs remind the powerful men in the royal family of their previous love.

The FLs are constantly exposed to threats in the harem.

While watching this Drama it often reminded me of Empress Ki. It's the same type of story about the palace and plotting and backstabbing in the harem and which effects it has on people living through it. Empress Ki compared with Legend of Zhen Huan is a bit lighter though

Ruyi's Royal Love in the Palace is the sequel to Zhen Huan. But both are harem dramas and they can be watched without having to watch the other.
Zhen Huan covers the harem of emperor Yongzheng and in Ruyi, Yongzheng's son, Qianlong, rises to the throne and the story focuses on Ruyi, a consort of his harem.

Okay! In account of the origin of the plot I would say that there's nothing comparable between two the two dramas. It's a different dynasty, different storyline but one thing strongly is attached to both dramas which is the female centered plot and the sisterhood between the leads. I you like ADOS I'm sure you would like Zhen Huan as both stories portrayed a Zhao Pan'er and Zhen Huan trying to find their ways and never admit defeat alongside protecting there closed ones with all it takes!
The two leads are really alike in strength whiteout wielding a sword and smartness in their business (Zhao Pan'er) and harem (Zhen Huan).