Sync method names follow the following logic.
"eventSync<Origin><Operation><Destination>".
Depending on the provided destination the method is located in the class EventSyncCivicrm (destination: CiviCRM) or EventSyncDrupal (destination: Drupal).
Examples: event_sync_civicrm_create_drupal is called when an event in civicrm is created and must be synced to drupal and is located in class EventSyncDrupal.
event_sync_drupal_delete_civicrm is called when an even in drupal is deleted and must be synced to civicrm and is located in class EventSyncCivicrm.