Can customers choose between Standard and Express shipping in the same zone?

Yes. Go to Plugins → Shipping Zone and click Edit on the zone.

1. Under Shipping methods, click + Add method once for each option.
2. Give each one a Label customers will see, like "Standard (5-7 days)" or "Express (1-2 days)".
3. Pick a Type for each, for example Flat rate, Weight-based (brackets) or Free shipping, and set the cost.
4. Optionally set Free above cart total on a method.
5. Keep Enabled ticked and save the zone.

At checkout, customers in that zone see a Shipping method list. Each option shows its price, or "Free", and they pick one.