Thank you Erel, it is working but with a twist...
If I call this immediately after loading the webview, it does not work. Apparently the webview is a separate process and you have to wait until it's done before calling the zoom.
I set a delay (using a timer) to call the zoom function a certain time later after loading the data and that works, at least on this phone and with the small amount of data I am displaying at the moment.
I am concerned that on a slower device, or with a lot more data to display, the delay I set may not be enough. 500 mS seems to work, I tried 300 initially and that was not enough.
It would be nice if there was a way to set a callback so that the zoom would be called when the webview has finished loading.