作 zuò = 亻 (rén, person) + 乍 (zhà, the phonetic). It is a pictophonetic compound: the standing-person radical 亻 supplies the meaning, a human being engaged in activity, and 乍 supplies the sound. The right-hand 乍 originally meant "to begin, all of a sudden," so the early sense of 作 is a person setting something in motion, starting an action. From "to begin doing" the meaning broadened to the whole field of doing, making, and producing.

Three threads run out from that core:

1. To do, to engage in. Activity in general: 工作 gōngzuò (to work; a job), 作业 zuòyè (homework; an assignment).
2. To make, to produce, to compose. Bringing a thing into being, especially a crafted or written one: 作品 zuòpǐn (a work), 作文 zuòwén (a composition), 写作 xiězuò (writing), 制作 zhìzuò (to produce).
3. To act as, to regard as. Taking on a role or treating one thing as another: 作为 zuòwéi (as; conduct), 当作 dàngzuò (to treat as), 看作 kànzuò (to regard as).

The thread is purposeful making. Where its everyday cousin 做 zuò handles the concrete, hands-on doing of ordinary life, 作 leans toward the formal, the literary, and the abstract: composing, producing, and acting in a capacity. The two words share a sound and overlap heavily, which is exactly why their division of labor is worth learning.

This is where 作 sits closest to its literary heart. To 作 is to compose, to bring a crafted thing into being: a 作品 zuòpǐn (a work of art or literature), a 作文 zuòwén (a written composition), a piece of 音乐 written by a 作曲家 zuòqǔjiā (a composer). The maker is the 作者 zuòzhě (author) or 作家 zuòjiā (writer). Here 作 keeps the dignity of its older sense, the deliberate act of creation, distinct from mere doing.

This creative weight is why 作 rather than 做 fills the vocabulary of the arts and letters. You 做 a meal or 做 the dishes, the hands-on chores of the day; but you 作 a poem, 作 a painting, 作 a symphony. The same falling-tone sound splits cleanly along this line: 做 for the concrete and ordinary, 作 for the composed and the made-to-last.

See the person 亻 on the left and read 乍 as the spark of beginning: a human being who sets something into motion. That is 作 at its root, to start a deed and carry it through to a made thing.

Follow the spark in three directions. Bend it toward labor and you get the daily job (工作) and the assignment (作业). Bend it toward craft and you get the composed work (作品) and its author (作者). Bend it toward role and you get acting in a capacity (作为) and treating one thing as another (当作). And when the doing is plain and physical rather than composed, the language hands the task to its twin 做. Keep that division in mind, and the two zuò will never blur.