These phrases mean the same thing and can be combined into a single phrase. Alternate translation: "you will plan to do something very evil" (See: [[rc://en/ta/man/translate/figs-doublet]])
Here "heart" refers to his thinking. This can be stated in active form. Alternate translation: "you will think of plans" (See: [[rc://en/ta/man/translate/figs-metonymy]])