I've disabled the captcha option in the contact form extension (Zenphoto 1.5.3) because when you try to mark the "I accept ..." box, it opens ... the captcha picture box. If Captcha has been done, it's hard to mark this box; without accepting, message cannot be sent.

I am sorry I can't reproduce any issue with captcha trying it here https://www.zenphoto.org/pages/contact/ on our own site:

Yes, there is something wrong on my side, but you also have a problem, look at the generated code : your site's captcha iframe includes [code] and [/code]elements

Full picture

What I see from the screenshot this is not an official theme so I can only assume this is a theme issue.

but you also have a problem, look at the generated code : your site's captcha iframe includes and elements

No, that's correct as It's an iframe which of course contains a full page which is loaded from Google's captcha service.

This needs some CSS change.
If you can enable reCaptcha I can have a quick look.

My guess is that you need to add
.g-recaptcha {display: inline-block;}
to your
.../themes/basic/styles/dark.css file