On API >= 11, you can use:
wv.getSettings().setBuiltInZoomControls(true);
wv.getSettings().setDisplayZoomControls(false);
As per the SDK:
public void setDisplayZoomControls (boolean enabled)
Since: API Level 11
Sets whether the on screen zoom buttons are used. A combination of built in zoom controls enabled and on screen zoom controls disabled allows for pinch to zoom to work without the on screen controls