Stake it and see what happens.

If the damaged one still looks stressed, I would just cut it off and leave the one good plant.

Pretty normal for Zucchini to eventually tumble off to the side. You can try to support it some, but it never will look decorative.

Looks like you have damage from the dreaded squash vine borer.

https://extension.umn.edu/yard-and-garden-insects/squash-vine-borers#:~:text=Damage%20caused%20by%20squash%20vine%20borers&text=Wilting%20may%20occur%20only%20in,the%20base%20of%20the%20plant.&text=Several%20borer%20larvae%20may%20attack%20a%20single%20plant.

You can treat the area with permethrin or Sevin. Sevin is not for organic gardens.

Besides the the vine borers, I would consider repotting into a bigger container. Mine was in a 17" self watering pot, when it started to constantly look wilted. I reported it into a 24" self watering pot, and it is loving it! Before transplanting, I prepared the pocket of soil with Neptune's Harvest liquid fish fertilizer. After dropping the plant in, I added more soil, then watered it in. I then fed it a bit more of the fertilizer. It is thriving now! I swear it doubled in size within a few days!

Yes, you have squash vine borers. Consider a different crop.