The translation table is ONCE in the memory. Within Zend_Translate !
I don't know what you are expecting, but Zend_Translate translates your input, and Zend_Form creates a form... this two components are not related to each other.
Also why should Zend_Form hold an translation table ?
I would be interested in how you measured that there is 11 times more memory consumtion than without Zend_Form.