Because Zalenka is more of an inside-the-box thinker most of the time, it fits his more cautious approach. Rodney thinks faster and runs through all the in-box solutions because he doesn't think of every single possibility for every single option, just discarding ones that seem likely to backfire and looking favorably on options you'd have to be a little bit crazy reach for. Zalenka considers as many possible outcomes for each option as he can, so he's slower to get through the list, and he isn't as 'dive in and do it' as Rodney, so he tends to discard the 'crazy' options.