I wouldn't recommending doing that, their digestive system is pretty delicate so switching food should be done slowly over a few weeks if possible. The recommended way to switch is 1/4 per week, so 1/4 new 3/4 old the first week, if no digestive upset then you can do 1/2 and 1/2 the next week and so on. Some chins even end up needing gas drops and probiotic when switching foods to help their gut adjust, so ideally it's best to just pick a pellet that works for your chin and stick with it.
What you can switch up though is the hay, although timothy hay should be the primary hay you can also give other grass hay like orchard and meadow hay daily, grain hay like oat about a handful worth a week, and alfalfa can be given as an occasional treat. You can also give treats a couple times a week too, here is a list of currently recommended treats (it's from a FB group I am in, they recently updated it) Oh and keep in mind that recommendations on things do change, sometime we find that things aren't as bad as we thought so they are ok to give, or find out that they do harm long term and stop recommending them.
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Also a word of caution with Mazuri, it's not as highly recommended anymore since it does contain oats, which can cause gas, as well as whey (a milk byproduct) so it can cause digestive issues for some chins. These things are not new, it just seems more chins are now having a problem (I was told in the past it's likely genetic since it seems to just effect certain breeding lines, my guess they are likely unable to digest the whey), but if your chin does well on it then it's still a good food.
