There's no single "4x4 switch" in the sense of a single button or lever to engage 4x4 in a 1995 Chevy Z71. Instead, it uses a transfer case with different shift positions selected via a floor-mounted lever or rotary dial (depending on the specific options). This lever typically engages either 2WD, 4HI (4-wheel high), and 4LO (4-wheel low).
To find it, look on the floor, near the driver's seat, typically between the driver and passenger seats. It'll be a lever or a rotary dial with markings indicating the different drive modes. The exact position might vary slightly based on other options in your specific truck.
