Although this isn't a Z example, I will give you some recent experience I had with my 71 Chevy truck. When I repainted I needed a new hood (old one rusted beyond repair), so for only a couple of bucks more, I put on a cowl hood (more for looks than anything...just something different).
The other morning I went to the store. There was a good layer of water on the truck (condensation from the evening's chill). I have a pretty good layer of wax on the truck so the water beads up nicely.....
Anyways: Even at fairly low speeds (<50mph), I noticed the drops of water running up the cowl, and being drawn (sucked) pretty briskly into the air gap of the cowl induction. The droplets from the windshield cowl (part that covers the wiper mechanism) also were pulled forward into the hood gap. That experience sold me on the "working" of the cowl hood......
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Just my 2 c worth