Is there a button on the Wacom one which you can set to zoom when in Fresco? I found the following on a Wacom help page, can not guarantee it is for your specific device though. Pans or zooms, depending on whether you are hovering or touching the device surface.
To pan, hover above (but do not touch) the device surface, and then press and hold the button while moving your pen.
To zoom, press and hold the button while touching the device surface and move the pen towards the top to zoom out or towards the bottom to zoom in.
If you pick up your pen to hover, zooming stops. As long as you continue to hover and hold the button, you can still zoom when you touch the pen tip to the surface again.
If you want to pan again after zooming, release the button and press it again.