The 10pm curfew is normal on most German airports but usually these other airports have exceptions such as "Home Base carriers may land scheduled until 11pm and delayed until midnight" or similar.
Almost all German airfields have strict closure times, but none (unfortunately) have the above allowance. Having said that they do give extensions - although they require so much info its sometimes easier to get a mortgage
A 20z closure is mighty early though - no wonder EZY are struggling to make it work
