Zabbix agent log entries have "LF" ("Line Feed", #10 ASCII) symbol at the end of the line, which does not work with older versions of standard Windows application "notepad". Notepad requires both "CR" ("Carriage Return", #13 ASCII) and "LF" to be present at the end of the line in order to start displaying the next entry from the new line.

Such a behaviour has been recently changed by Microsoft - https://devblogs.microsoft.com/commandline/extended-eol-in-notepad/ , however it only affects the most recent OS editions.

Please, consider adding a possibility to change Zabbix agent log end of the line symbol sequence. Other possibility would be to detect Windows OS and set the correponding end of the line symbol sequence automatically.