Can you mix slim fast diet with weight watchers?

Just wondering can you mix the slim fast diet with weight watchers... I am currently having a slimfast for breakfast, a weight watcher meal/sandwich for dinner and on a night i am havin a weight watcher meal... also with fruit and slim fast snacks in the middle and water for drinks... is this ok to lose weight?? I also do 30 mins of exercise most nights! Any help would be appreciated.