well, since your always going outside, that is the first step to success. You can try clicker training when they do go potty(never personally tried it). We associated words with going to the door to go potty. First say potty, usually it ends being in a high pitched voice haha, then doing the constant potty break thing. Then hopefully they associate the high pitched potty with going and obviously praise when they do. Then you can tell them when they need to go. also, on top of the constant potty breaks, when zoee goes, take taggart out too. HOPEFULLY taggart can catch on and see that zoee goes to the door to go potty, then will think, I get it!
It took bayley a long time to get the trick, but slowly letting them out together and randomly asking if she has to, go she picked it up!

potty training is tough.. i wish you luck. Thats the steps we all took.. hope it helps some!!!