Why does the beer batter seem to hold too much oil

160C sounds about right for cooking oil temp. I typically shallow fry on the stovetop for about 10-12 minutes for the thighs and then transfer them to a 175C oven to finish cooking (if needed) and then repeat with the breasts. I would stay away from "battering" if you are looking to replicate something like popeye's.

A few things I do to ensure a nice thick crunchy crust:

1. Put your flour (seasoning or not thats up to you) in a very large zip top bag or paper bag will work too so that when you put the chicken in you can "tumble" it around to be coated like in a dryer. I find that this is cleaner and more effective in creating a crust.
2. pull out the dredged chicken, redip it in the buttermilk and then throw it back in the bag to tumble.
3. let the chicken rest on an elevated rack for 15-20 minutes (up to an hour ideally) to allow the dredge to set and adhere to the chicken well. This helps prevent the dreaded "skin falling off the meat" phenomenon.

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.