If you would like to recover those deleted messages from ZTE ZMax, you can apply Android Data Recovery which supports to recover lost data like contacts, messages, videos etc. Just launch it and connect your phone to computer, you can recover the data as like. On the other hand, you need to be patient to wait for analyzing process.

Every time I attempt to delete a thread of messages on my phone, the screen just freezes for a long period of time, then a notification pops up that informs me that messaging has stopped working and the screen goes black. It will not let me reopen messaging until I restart the phone, and it does not remove the thread that I attempted to delete. Any suggestions?