Was supose to be black beauty Zucchini. Looks like a pumpkin forming on a zucchini plant. Round zucchini? there pretty big though and getting bigger.
These are plants from the same batch of seed but look different coloured.

It could be a RONDE DE NICE however I have not seen it that color
Maybe a cross with another zuc.
You may have a new variety
I would save it's seeds

Looks to me like an "Eight Ball" zuke. They get about softball size for best flavor but if left to grow they'll get a tad bigger.

Shoe

this is what inside looks like. Sort of reminds me of a not formed pumpkin..are pumpkins green before they go orange? Smells like a pumpkin but could be a zucchini?

Did you ever find out for sure?

no think i have another one forming by its self in my garden now, id forgotten about it until you posted again.

Bush or vine? several of the green round zukes look like your photos. The bottom photo is a dead ringer for Lucky 8. Second photo appears to be a bush, so I expect you have one of the green round zucchini.
Lucky 8


Eight Ball

Tonda diNizza/Ronde de Nice

Cue Ball

i just looked and what i have coming up is not like before, yes the one in the beginning of this post would be a zuccini i guess. thanks horseshoe and farmerdill but now i have this one that came up by itself. Looks a bit like a rockmelon, its a vine.

Cantaloupe?

You have a lot of volunteer seeds in your garden there!