I want to print the grid with a zoom level, what should I do?

You can override GetZoom() and return a zooming factor depending whether the grid is in print mode or not.  You should check IsPrinting() to determine if the grid is in print mode.

However, GetZoom() is not a real zooming. The SetZoom()/GetZoom() API in OG only changes the font size so that you get the impression the view is zoomed.

For printing only, a better idea is to take a look at the "Fit To Page" sample in the customer area on our web site. It shows you how to change the mapping mode and scale the printout with a given zoom factor.