Complex sentence: Chinese dialects continually interact and influence each other regardless of whether it is a forcibly imposed official dialect or a neighboring one, and indeed diglossia is the norm throughout most of the world, so it's only natural that such contact would influence both.
Split into simpler sentences: Chinese dialects continually interact and influence each other regardless of whether it is a forcibly imposed official dialect or a neighboring one. Indeed diglossia is the norm throughout most of the world, so it's only natural that such contact would influence both.