Deep frying - beer batter vs. bread crumbs
As SAJ14SAJ mentioned, when doing a batter coating, you need to hold it in the oil for a second before letting it drop, so that it'll crust up before it touches the basket.

However, you also mentioned 'with some zucchini slices on top', I suspect that the batter came off entirely.

Breading for frying is a bit strange, as you need to make sure that you don't put something wet on top of something else wet (or dry on dry), and no layer too thick.

So, in the case of the zucchini, you need to make sure that the pieces are very dry before putting them in the batter ... if they're freshly sliced, they'll extrude liquid, and so you may need to coat them in flour or starch, shake them off, and then put them in the batter.