苦心积虑 is an idiom

苦心积虑kǔ xīn jī lǜ

积虑：长期地或一再地思考。费尽心思长时间的思考问题。

Example 奇逢谓其～，阅历深而动忍孰。《清史稿·文苑传·申涵光》

Word breakdown for “苦心积虑”: Open in Reader →

苦心HSK 7–9

1.painstaking effort2.to take a lot of trouble3.laborious at pains

积積HSK 7–9

1.to amass; to accumulate; to store up2.(math.) product (the result of multiplication)3.(TCM) constipation; indigestion

1.to think over2.to consider3.anxiety