[subject] + 不仅 + [A],而且 / 还 / 也 + [B]
不仅 + [subject 1] + [A],而且 + [subject 2] + 也 + [B]
不仅如此,[sentence]
不仅 opens the first clause and 而且 the second: A is true, and B – usually the bigger point – is true as well. It means the same as 不但…而且 and is a notch more formal, at home in writing, presentations and news.
In the second clause, 还 or 也 can replace 而且, or join it.
With one subject for both clauses, the subject comes first and 不仅 follows it. With two different subjects, 不仅 goes in front of the first subject, and each clause keeps its own.
不仅如此 "not only that" opens a new sentence that adds to the one before.