This diagram will illustrate what I mean.
This is a typical word-for-word translation. We in Japanese do not prefer non-animate object such as a diagram to be used as a subject with an transitive verb. It sounds unnatural.
Also, translating “will” as ～でしょう in this context is awkward. "Will| in the English sentence implies that what I mean is not understood by someone yet, but the person will understand once see/read it.
My alternative translations are:
この図をご覧頂ければ、私の意図がご理解頂けるかと思います。（このずをごらんいただければ、わたしのいとがごりかいいただけるかとおもいます）= (lit.) Once you see this diagram, you will understand what I mean.
私の意図は、この図で説明できるかと思います。（わたしのいとは、このずでせつめいできるかとおもいます）= (lit.) I believe my intent can be expressed by this diagram.
The first sentence is used when the speaker (I) are directly speaking to the other person(s) who are supposed to understand my intent.
The second sentence implies that the other person(s) who are supposed to understand my intent are not available here; it’s more like I am talking with my supervisor as a third person about how good this diagram is.