I would suggest https://www.bestbikesplit.com/ I think you can try at least one course with the free account, but I have a paid account and I say its worth it. Both for training, and race day planning. There is a deal if you have TrainingPeaks
Basically it will allow you to enter the course and your FTP and it will take into account everything from grade/wind/road surface, etc and output a power plan to get you through the course as fast as possible within you target power. Typical target power would be 65 - 75% of FTP. You can output this power plan as a workout to Zwift so you can simulate the race and see if you can hold your target power.
I did exactly this for the huge hill on the Ironman 70.3 Nice course last year - basically did a workout on erg mode that was my target power to see how it felt. It allowed me in the actual race to know exactly what my power target should and the confidence that I could hold it for the whole time. If you’re accurate with all the parameters you’re entering and execute the plan during the race it’s scary accurate on your finish time too. On a couple races now it’s predicted my finish time within 2 minutes.