Looks like another instance of the squash vine borer attacking the stem.

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.

I'm not sure if its borers because there are no eggs under leaves and the plant continues to grow. I think it's the stress from getting to heavy but i don't know what to do about it

It sounds like you are confusing 2 pests.

The squash vine borer lays it's eggs directly on the stem. The egg hatches and the worm burrows into the stem and eats it from the inside. The adult is a moth that almost looks like a large wasp with a orangish/red body.

The squash bug lays it's eggs in clusters on the leaves. The nymphs then suck the juices from the leaves. The adults look like elongated stink bugs.

Since the stem seams sturdy I would agree it's not caused by squash vine borer. If the zucchini is already growing then I would say it has already flowered.

Borers are not a stage in the life cycle of squash bugs. Squash bugs are the insects that lay the eggs you see in clusters under the leaves. They hatch into wingless nymphs which molt a few times before becoming adults bugs (true bugs, Hemiptera) with wings.

The adult squash vine borer is a clearwing moth that resembles a wasp with a red body. The female lays single eggs at the base of squash stems. They fly fast and don't stick around after laying their eggs. It is easy to never know they visited your plants. When the egg hatches the larva bores into the stem. Sometimes the plant will continue to grow, especially if you slit the stem and remove or kill the larva. Sometimes there may be more than one. Pesticides like Cindy suggests are most effective on adults or eggs, larva - not so much

I don't see lots of frass in your photo. Perhaps you only have a broken stem. Check to see if there is any moist sawdust-like material by the stem. That would be the frass (caterpillar poop).

Vine borers also lay eggs but not in clusters, they will be further apart on the leaves or the base of plant. If already hatched anf you see a hole on stem you can slice open the stem and locate the borer larvae and remove it then cover the split stem with soil. I just did this on mine.