What is the difference between zero-cross triac couplers and non-zero-cross triac couplers? How should they be used properly?

Zero-cross (ZC) triac-output photocouplers are provided with a function for not performing ON operation while the AC power supply voltage is high, whereas non-zero-cross (NZC) triac-output photocouplers can perform ON operation when the AC power supply voltage is at any level. ZC triac-output photocouplers cannot trigger ON operation while the power supply voltage is high, so they can prevent the occurrence of radio noise. However, since they can perform ON operation only while the power supply voltage is at a low level, they cannot perform phase control intended to control the amount of electricity.
Refer to Toshiba Application Note "Triac couplers-basic properties and application design", sections 10.1 to 10.3. as well.
(https://toshiba.semicon-storage.com/ap-en/semiconductor/knowledge/application-note.html)