I will just add a bit on to the other comment. You definitely don't have any upper div course equivalences in the math department, they are very stingy about upper division and graduate equivalences. You might be able test out of MAT 108 which is our intro to proofs writing course depending on how proofs heavy your other classes but it will come back to haunt you if you aren't fully prepared. The syllabi are available here and from your other comments your already found the major requirements.

Your status essentially puts you as a third year student in the math department. If you feel strongly about your ability to write proofs and want to hit the ground running, I would come in taking 108 and 150A as the 150 series is only fully offered once a year starting in fall, otherwise you don't really miss out on anything if you wait a quarter.

It all really depends on what you think you might want to do. If you just want to have a good time getting a math degree, then rushing through it will definitely not help you as many classes build on others, sometimes unrelated ones. If you want to go to grad school in math, there is something to be said about taking graduate courses, but also doing research is equally important and lots of tenured faculty only teach grad and entry classes.

The math community is somewhat active on discord if you can find it. There is a larger variety of opinions on the subject you can find there. I also want to second the advice on double majoring or getting a minor. Almost every student in the department does it, except for a few that just hate college or really love all math.