involving a lot of different parts, in a way that is difficult to understand

complicated instructions 复杂的指令

I had to fill in this really complicated form. 我必须填写这张非常复杂的表格。

The rules are rather complicated to follow. 这些规定遵守起来挺复杂的。

The relationship is a bit complicated. He's my mother's cousin's daughter's child. 关系有点儿复杂，他是我母亲的表姐的女儿的孩子。