I'm so sorry, I thought you were a man, 
I have a small suggestion. On the contact us page, add a read-only judgment for the contactname option on the guest account. I am currently doing this, but I don’t know if there is any other better method.
HTML Code:
includes/templates/template_default/templates/tpl_contact_us_default.php
PHP Code:
<?php if (zen_in_guest_checkout()) { ?>
<?php echo zen_draw_input_field('contactname', $name, ' size="40" id="contactname" placeholder="' . ENTRY_REQUIRED_SYMBOL . '" required'.' readonly="true"'); ?>
<?php } else { ?>
<?php echo zen_draw_input_field('contactname', $name, ' size="40" id="contactname" placeholder="' . ENTRY_REQUIRED_SYMBOL . '" required'); ?>
<?php } ?>
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