I love this tip. Here’s how to do it:

• Bring up Apple Maps.
• Double-tap in the map, but on the second tap, don’t lift your finger. So tap-lift-tap-leave.
• Now slide up or down to zoom in and out.

This also works with Google Maps but, interestingly, it works the exact opposite way. On Google Maps, slide up to zoom out, down to zoom in.

Here’s an Apple Support document that contains this tip and a ton more iOS 11 chewy goodness. [H/T Fabrice Dubois]