Enable Safari Zoom by Script
This Applescript code sets the zoom level globally:

tell application "System Events"
    tell application process "Safari"
        set frontmost to true
        keystroke "," using command down
        delay 0.5
        tell window 1
            click button "Advanced" of toolbar 1 of it
            click pop up button 3 of group 1 of group 1 of it
            click menu item 4 of menu 1 of pop up button 3 of group 1 of group 1 of it
            keystroke "w" using command down
        end tell
    end tell
end tell


change menu item 4 to 5 for a 115% or 6 for 125% zoom level.

Using an Applescript is better than using cmd + / cmd + - because it sets the default zoom for all pages.