Most importantly, you should not use sunscreen containing DEET (or vica versa), since it has been found to result in applying too much DEET. The other thing that you should know is that something like 6+% of applied DEET is absorbed through the skin and sunscreen may affect this, so best to put on the sunscreeen and let it dry some before applying DEET. Finally, there are diminishing returns to using products with more than 30% DEET and no advantage to using anything above 50% DEET. Higher amounts of DEET increase the duration of effectiveness, they are not more efffective in keeping mosquitoes from biting.
