I think that what is uniquely Zen about Zen (as opposed to other equally rich but different flavours of Buddhism), is its stubborn insistence that everything is innately perfect, without need for adornment or improvement.
Those stock images of a rock, a stalk of bamboo, a dew drop on a leaf…they are clichés of course, but they tell the story. The story is of what makes the rock worthy: not its roundness or gloss or smoothness, not its symbolic patience or solidity or charming asymmetry. What makes the rock beautiful and worthy, is its rockness – and even to say rockness is to make an adjective out of a noun, thereby missing the point. The point is, that words and concepts cannot describe what is already perfect beyond words.
This deep respect for the innate nature of all things applies equally to people: what makes us buddhas is not our kindness or intelligence or learnedness or beauty, nor our skills or accomplishments. We can relax: there is nothing we need to do or be. What makes us buddhas is just the fact that we are—and that, in itself, is awesome and complete and totally deliciously delightfully Zen.