Hey StaceyD,
We really don’t recommend merging plans – it can get very messy and potentially lead to overtraining.
Without knowing all the details on the importance of these races to you, and your fitness/training history – my short answer would be to focus on your marathon training, and supplement with 2 swims per week, replace 2 of your runs (not your long run) with a bike session of similar intensity + 20% volume and obviously keep the rest of your runs as is. You will need a full week of rest after the marathon, potentially even 2, then you can return to swim and bike, and very short easy runs. This approach will take you all the way up to the Triathlon. Again this going to be depend on may things such as your racing experience and fitness level and how hard you ran the marathon.
The best way to supplement workouts into a plan is to to use our subscription service that comes with the workout library so you can drag and drop workouts into your calendar as needed.
Cheers
Leyla