Hi, Martin,
Do you want to generate 24MHz and 6MHz signal with 12MHz signal or generate 12MHz and 6MHz signal with 24mHz signal?
If you want to generate 24MHz and 6MHz signal with 12MHz signal, it is impossible without FLL or PLL.
If you want to generate 12MHz and 6MHz signal with 24mHz signal, it is okay with FTM of Kinetis(K40/K60/K20/K10...) or eFlexPWM(KV family).
Hope it can help you
BR
Xiangjun Rong