Everyone throws differently, and these two guys are able to get away with breaking the "rules".
Generally you want to land with your toe pointed to your target, but if you're repeating your stride, throwing strikes, at your peak potential velocity, and not feeling any pain, then it doesn't matter so much how your front toe lands. If Zumaya or Verlander have issues with their control, for example, their pitching coach might look at their front toe as part of, or a symptom of, a problem. Otherwise, as long as they're healthy and effective, there's no reason to change it.
At the same time, for young pitchers who are still learning about mechanics and trying to repeat them, it's better to try landing straight than trying to emulate what these guys are doing.