so there is a new race series on zwift, for those lucky enough to have access to a treadmill as well as the trainer. https://www.zwift.si/
unfortunately right now it is set up as 3 different events, rather than one continuous race. hopefully in the future zwift can reformat the event to be a single race. as of now its a little tricky to figure out, but worked well for my first try. you pick your first run based on what pace you will hold x 2 miles. then that should give you roughly 5 minutes after finishing the run to set up the bike portion and join that event. when you are done with the bike you join any one of the 4 final runs, which are staggered starts to make sure everyone can finish the bike and get into one of the runs. downside is you're never sure who you're racing against, and joining the A bike race is a big overall time advantage. you could also do the A bike race, take a long and relaxing T2, and join the D final run race with no penalty. Ideally zwift will come up with a seamless way to switch R/B/R and have the racing experience be more head to head, and realistic. Also this opens up the door for zwift Tris, when they finally get around to supporting rowing/kayak/swim erg avatars and courses.

edit: i should add that this is not put on by zwift at all, but run by single fellow who has put in all the work to make this happen. it's worth trying out and showing some support so that zwift realizes this is a cool thing and actually puts some programming time behind it to make a finished product.