Piece of cake walk in the park

Something that's extremely easy. A combination of the phrases "Piece of cake", "Cake walk", & "Walk in the park", all of which mean something that's very easy. A piece of cake is a piece of cake & a cake walk is walking with a cake, so a piece of cake walk would be walking with a piece of cake. A walk in the park is walking in the park, so a piece of cake walk in the park would be walking in the park with a piece of cake.

I wasn't fazed by Fukouna Shoujo 03. It was a piece of cake walk in the park.