Read the following articles for more information:
- Log file monitoring: https://www.zabbix.com/documentation/4.0/manual/config/items/itemtypes/log_items
- Calculated items: https://www.zabbix.com/documentation/4.0/manual/config/items/itemtypes/calculated
- Aggregate checks: https://www.zabbix.com/documentation/4.0/manual/config/items/itemtypes/aggregate
- SSH checks:https://www.zabbix.com/documentation/4.0/manual/config/items/itemtypes/ssh_checks
- Telnet checks: https://www.zabbix.com/documentation/4.0/manual/config/items/itemtypes/telnet_checks
- Dependent items: https://www.zabbix.com/documentation/4.0/manual/config/items/itemtypes/dependent_items
- Creating an item: https://www.zabbix.com/documentation/4.0/manual/config/items/item?s[]=hexadecimal&s[]=decimal#item_value_preprocessing