Complex sentence: He realized that a lever, pulley, and wheel and axle are in essence the same device; a body rotating about a hinge, and that an inclined plane, wedge and screw are similarly a block sliding on a flat surface.
Split into simpler sentences: He realized that a lever, pulley, and wheel and axle are in essence the same device: a body rotating about a hinge. Similarly, an inclined plane, wedge, and screw are a block sliding on a flat surface.