"To mix the forms" means to combine different types, styles, or formats of something together. It involves blending different elements or components to create a new or diverse composition. Full definition
They've been in pretty mixed form at this ground so far, winning six of their 14 home league matches. (latestchelseanews.com)
They argue that the apparent existence of mixed forms of diabetes exposes a fundamental flaw in the way we classify and treat the disease. (newscientist.com)
But, he adds, «On the other hand, however, there are also such mixed forms as an empiristically grounded theology.» (firstthings.com)