is there a way to select a route for an existing workout (training peaks) vs the zwift route selection?
Not sure I understand your question. Once you log in to zwift and get to the world screen you have to choose a Zwift route to ride. Below that there is the workout selector where you can select what workout you want to do. Either way you need to select a Zwift route to ride for your workout.
Are you asking about a Zwift route or a Zwift workout? As stated a Zwift route must be selected to go along with a workout. The route is the roads you will follow.
If you are asking about importing a Training Peaks workout to do within Zwift I do not know personally. I have never done this. A quick internet search makes it look as though it is possible be linking your TP account. Then it is a simple import.
I use training peaks and it seems like Zwift choses the route. Sometimes I’d like to select my own training route. Will pay more attention next time to see if I’m missing a step.
Brian Fisher
"Life begins when you reach the end of
your comfort zone."
(Please excuse my spelling and inadvertent typos).