I read this on URL:
http://docs.oracle.com/cd/E17952_01/refman-5.5-en/optimizing-myisam-bulk-data-loading.html
If you lock table before you insert and unlock it after that. The speed will increase 40% faster than not locking.
I don’t know if Zend Framework does lock table before insert or not?
If you don’t experience any performance issues with your application – don’t do that. If you do experience any performance issues – start with profiling and finding the exact reason of your issues.
PS: that phrase in mysql documentation is very speculative.