I haven't done any style changes in ages since my downtime is dedicated to comic stuff, but I've dabbled around before.
My usual style, current and 2014:
CW: Blood


Whatever this style is from 2008-2009.

Sorta realism/surrealism 2010 and 2015:


Chibi 2011:


Simplistic-ish, 2023:

Whatever this Waluigi, Junji Ito mashup is, 2018:

I would say these look fairly similar, but if I really wanted to I could dabble in a larger variety of styles. I also wouldn't say it's "hard" necessarily, drawing is too relaxing to find hard, on the other hand successfully pulling off a style change... Well. Style studies overall are really fun, especially if you're doing them to see how you would draw your characters in other artist's styles.

(2017, from the top left! 1. Mine, 2. Moth, creator of Raining Knives, 3. Jay Fabares, artist for The Pale, 4. I belieeeve this is Mirre's style, creator of Tunes of Lycka, 5. Sarah N., creator of Daniel, The Devil's Trill and other comics.)