Keep things friendly. Let them know you appreciate their offer, but you have put a lot of time into developing a Nissan Z site for that domain. I say stick with your original offer -
"I appreciate your offer to purchase zride.com for $200. Unfortunately, this domain name is very valuable to me, as I have put a lot of effort into developing a Nizzan Z site which will soon go live on this domain name. I am not prepared to abandon the effort I've put into my Nissan Z site for less than US $2000. I have been advised that your trademark does not come into play since I registered this domain before your trademark was filed. Please feel free to contact me if you would like to continue discussion of this matter, however, please don't delay. Once my new site is up, I will be very reluctant to sell this domain. Thank you."