Tell me zigbee is more reliable than this [Devices offline]

Zigbee has much shorter range due to worse radio propegation than Z-Wave because Zigbee 2.4GHz and that means that you are going to need to make sure that you add many more ”good” Zigbee Router devices and spread them out yet seento it so they are in range of each other. If you read, understand, and follow all these tips then you should be fine → Zigbee networks: how to guide for avoiding interference + optimize using Zigbee Router devices (repeaters/extenders) to get a stable mesh network with best possible range and coverage