I forgot to mention. I also sculpted that plastic rocket in zbrush using masking with curve brushes and inflate. It was incredibly easy and effective to make that details in zbrush!
Love it concept and render. Very Well done! 
excellent work, could you kindly explain this use of masking with curve brushes and the alphas used ?
Explaining your workflow would help me to get a better feel for Zbr…I like both the concept sketch and the Rockets… 