From the outset, we have to admit that zucchini is a very pleasant summer vegetable, but it doesn't have a very pronounced taste.
But in its early stages, when it's not too big, the taste is still there, with a delicious crunch.
The problem, so to speak, is that both the taste and the crunchiness will diminish, while the size will increase.
Put another way, the larger the zucchini, the less flavor it has, and the greater the volume of its center and seeds in relation to its flesh.
So what's the "right" size?
A great chef, Alain Dutournier, used to say that beyond 15 cm (6 inches), a zucchini is of no interest (gustatory).
The smaller the zucchini, the crunchier and tastier it is, so try to limit yourself to a maximum size of 15-20 cm.
There are 2 exceptions, however: 1) for stuffed zucchinis, you can go (a little) beyond this size, to facilitate filling with the stuffing, and 2) for a soup.
The larger the zucchini, the more seeds you'll need to remove from the center.
When the zucchini is small, you can't feel them, but in a large one, they have to be removed because they're too big/hard.
Even very small zucchinis, as big as your finger, are interesting.
A delight to bite into, dipped in a lemon mayonnaise for example.
Unfortunately, many amateur gardeners are unaware of this taste/size ratio, and allow their zucchinis to grow to impressive sizes, thinking they're doing the right thing...