How to Zoom in and Zoom out

WebDriver driver=new FirefoxDriver();

driver.get("https://www.google.co.in/");

WebElement searchtextbox=driver.findElement(By.name("q")):

//zoom in

searchtextbox.sendkeys(Keys.chord(Keys.Control,Keys.ADD));

//zoom out

searchtextbox.sendkeys(Keys.chord(Keys.Control,Keys.SUB));