Dear Employer,
I am Sam, a PHP developer have more then 7 years web development experience. I used zencart several time and I will able to implement the new theme on your existing zencart code base.
There should not be no issue as I will only change the html, css and images on the existing website. I will take total 20 days. 15 days for theme integration and 5 days for support. I am considering 15 days for theme integration as I don't know how much zencart script is modified by your previous dev.
Expecting long term business relationship through freelancer.com.
Waiting for your kind reply.
Best Regards,
Sam