$co_author = Array
(
    [ID] => 203
    [user_firstname] => Oliver
    [user_lastname] => Reppel
    [nickname] => oliver.reppel
    [user_nicename] => oliver-reppel
    [display_name] => Oliver Reppel
    [user_email] => oliver.reppel@accenture.com
    [user_url] => 
    [user_registered] => 2020-05-11 16:22:31
    [user_description] => 
    [user_avatar] => 
)

 $co_author = Array
(
    [ID] => 137
    [user_firstname] => Britta
    [user_lastname] => Kotthaus-Krahmer
    [nickname] => b.kotthaus-krahmer
    [user_nicename] => b-kotthaus-krahmer
    [display_name] => Britta Kotthaus-Krahmer
    [user_email] => b.kotthaus-krahmer@accenture.com
    [user_url] => 
    [user_registered] => 2019-08-26 14:27:51
    [user_description] => 
    [user_avatar] => 
)