These windings derive their names from the manner in which multi layer transformer windings are wound. Z-type windings (figure A below) decrease transformer primary capacitance therefore decreasing AC Primary side switching losses. It is recommended to use Z windings for applications that require low no-load power consumption and/or for high standby efficiency for a slight increase in leakage inductance and reduced bobbin utilization.
For other applications a simpler winding called C-type windings (shown in figure B below) can be used. C-type windings (shown in figure B below) are easier and quicker to wind at the cost slightly of lower efficiency and higher losses.