"That is a difficulty."
Translation:Dat is een moeilijkheid.
Moeite more refers to trouble/effort. You can say "Dat is een moeite", but you would say that when something is quite a bit of effort/trouble, not if something is a difficulty.
Can moeilijkheid be used for different strengths of difficulty? As in 'There is a low difficulty to this assault course', or 'What is the difficulty of that game?' Or is it an absolute idea (i.e. is it a difficulty or not?) Hope this makes sense!
You can use moeilijkheidsgraad for just any level of difficulty (it literally means difficulty level), but I'm not sure about just moeilijkheid. But, if Dutch is anything like my native language, Norwegian (and in a lot of ways, it is), then moeilijkheid only works as difficulty/problem, and moeilijkheidsgraad is what you need for other levels of difficulty.