debian:/usr/local/Zend/mysql/bin# ./mysqld 080627 12:31:16 [ERROR] Can't find messagefile '/usr/local/mysql/share/mysql/english/errmsg.sys' 080627 12:31:16 [ERROR] Aborting
This is for two reasons. First: you need to be up one level of directory to be able to run these commands. Some errors will tell you that but this one doesn't. Secondly, you need to use the mysqld_safe command.
debian:/usr/local/Zend/mysql# bin/mysqld_safe Starting mysqld daemon with databases from /usr/local/Zend/mysql/data
This works for me - I have no idea if it is the prescribed method but background the process above and you're good to go.