restore all mysql database from a –all-database sql.gz file

Yes. Generally, to restore compressed backup files you can do the following:

gunzip < alldb.sql.gz | mysql -u [uname] -p[pass] [dbname]

Please consult How to Back Up and Restore a MySQL Database

Note that the --all-databases option is applicable to backup only. The backup file itself will contain all the relevant CREATE DATABASE quux; commands for the restore.