the.com/walk in the park

means Something easy and effortless, requiring little struggle to accomplish.

from Rooted simply in the real experience of walking through a park — flat paths, pleasant surroundings, no obstacles — as opposed to, say, scaling a mountain. The phrase shows up in English by the mid-20th century as an idiom for something pleasant and undemanding; it's a plain metaphor more than a mystery, though no one can pin down the first person to say it.