Corey Hill Outlook is a small park on a steep pitch with the whole city laid out below it, and in late March the wind up there still carries an edge. That is when Brookline's yards come out from under the snow looking flattened and gray, and Zscapes Outdoor Services goes to work — raking out the winter, cutting back what died, getting a first pass down before the growth gets away. From there it is a steady season of cutting, trimming and cleanups until the leaves come down again. The turnaround is the fun part: three weeks between a matted brown yard and one you would set a chair on. Uphill streets, tight lots, enormous view — that is the ground here.