$ ${SOLR_ROOT}/bin/solr delete -help

Usage: solr delete [-c collectionName] [-deleteConfig boolean] [-p port] [-V]

The default behavior is to also delete the configuration directory from ZooKeeper so long as it is not being used by another collection.
You can override this behavior by passing -deleteConfig false when running this command.

-c collectionName
  Name of the collection to delete.

-deleteConfig boolean
  Delete the configuration directory from ZooKeeper; default is true.

-p port
  Port of a local Solr instance where you want to delete the collection.
  If not specified, the script will search the local system for a running Solr instance and will use the port of the first server it finds.

-V
  Enables more verbose output.

$ ${SOLR_ROOT}/bin/solr delete -c collection6 -deleteConfig false -p 8983

Here's the output of running this command on my localhost where I have 2 Solr instances and 1 ZooKeeper instance.

{
    "responseHeader": {
        "status": 0,
        "QTime": 220
    },
    "success": {
        "192.168.2.33:8983_solr": {
            "responseHeader": {
                "status": 0,
                "QTime": 40
            }
        },
        "192.168.2.33:8984_solr": {
            "responseHeader": {
                "status": 0,
                "QTime": 51
            }
        }
    }
}

Deleted collection 'collection6' using command:
http://192.168.2.33:8983/solr/admin/collections?action=DELETE&name=collection6

Notes:

• The collection will be deleted from ZooKeeper.
  
  
• For all the Solr alive instances, the collection folders (replicas) on the file system will be deleted.
  
  
• If you set the "deleteConfig" option to "true" (default), the Solr config will be deleted from ZooKeeper.