How can I send keyboard shortcut Alt + Shift + Z (hotkey) with Selenium 2?

You can check this question to refer about this - Pressing Ctrl+A in Selenium WebDriver

Check the answer which uses the chord method. In your case, you can do this -

String selectAll = Keys.chord(Keys.ALT, Keys.SHIFT,"z");
driver.findElement(By.tagName("html")).sendKeys(selectAll);

This can also be done using Actions keyUp and keyDown functions.

WebDriver driver = new FirefoxDriver();
Actions keyAction = new Actions(driver);
keyAction.keyDown(Keys.ALT).keyDown(Keys.SHIFT).sendKeys("z").keyUp(Keys.ALT).keyUp(Keys.SHIFT).perform();