Which programming is easy to understand? Android or iOS app development?

You are asking the wrong question. Both Android and iOS apps come with the same complexity level with distinct pros and cons. The coding has nothing to making an app development process difficult or easy. The things that massively differentiate difficult or easy programming is the way you have documented your app and its API. Also, the ease of learning an app development process depends on your background. 

·         If you have a background in Java programming or hands-on expertise on it, then go ahead to build Android-based apps. And if you are just entered into your app development journey, then going to learn iOS app development is a good option as the internet has more stuff and learning material available on iOS app development. 

·         If you have knowledge of object C, like old-style web projects or Mac programming, then go for learning iOS app development. 

·         There are numerous iPhone application development companies, offering part-time and full-time job opportunities on Android and iOS app development. You can get help with them to polish your app development skills more and become an ideal iOS app developer.