That is closer, but it's also not exactly correct. Now that I think about it, I don't think the English language has any sound where the letter "c" is used as it's pronounced in Croatian language. For example, the word "points" has the "ts" sound which is phonetically closest to the letter "c", but the the letter "c" is much sharper and shorter.
Edit: just as I wrote that, a word popped into my head which has almost the same "c" sound: Pizza. The "zz" sound, if you can call it that, is closer to the "c" letter phonetically than "ts". So Rimac would be pronounced something like Reemazz.
Edit: just as I wrote that, a word popped into my head which has almost the same "c" sound: Pizza. The "zz" sound, if you can call it that, is closer to the "c" letter phonetically than "ts". So Rimac would be pronounced something like Reemazz.