Please don't take this as being mean or rude because I am TRULY trying to say this as nicely as I possibly can
Honestly, it sounds like maybe both of your lives are just too busy for ANY type of breed of dog right now...Yorkie, or not. And puppies are puppies, they ARE going to have accidents - your babies are only 6 months old, so they probably AREN'T FULLY potty trained yet...it takes time. Also, as far as Yorkies being hard to potty train - I have heard this too - but I'm not sure why?? My little guy was a DREAM to potty train, lol...he really was! I had absolutely NO LUCK with my Mini Dachshund, and had to end up putting her outside in the backyard (she actually loves being back there anyway) because she would NOT stop peeing. So my Yorkie was MUCH easier!
I can totally understand you being frustrated, but honestly - IMO - it sounds like it just may not be working out over at your house
I'm not going to tell you to find them another home - but I am asking you to think about it. Maybe THEY would be better off being with someone who can offer them more "one on one" time....more attention.
Good luck in whatever you decide to do