In an R2-1 Two-Family, Medium-Density Residential District, no land or building shall be used or changed in use and no buildings shall be located, erected or structurally altered, unless otherwise provided herein, except for one or more of the following:
(a) Single-family dwellings.
(b) Two-family dwelling (up and down; side by side).
(c) Zero-lot line single-family dwellings. Units must be constructed in pairs which share no more than one common wall along a single side lot line.
(d) Accessory buildings incidental to the principal use which does not include any activity conducted as a business.
(e) Public schools.
(f) All other uses permitted in accordance with State and Federal laws.