Summer 2021 - Koffi is an extremely nice and affable professor, but that doesn't make up for how difficult it is to learn the material in his class. He goes over material extremely fast and skips steps all over the place, which makes understanding him through the live lectures almost impossible(I had to watch youtube videos in order to supplement the topics). The worst part isn't his bad handwriting or his really fast pace (even for a summer class) it's the raw amount of hw he assigns. He assigns 15-30 problems per lecture and they tend to be long, complicated, and harder than the tests problems. DO NOT wait to do these if you take him as he grades them for accuracy and they count for 20% of your grade. Overall I wish he was better at teaching because he is very excited for people to learn and did give a generous extra credit opportunity in the form of a real-world math project, however, this class can be much easier if taken with other professors.
Fall 2019 - Class attendance is not mandatory which is fantastic. Fan's first lecture did not leave a good impression, he basically just followed the textbook and sometimes gave confusing examples. I ditched all of the lectures after the first 2. I like this series which you can watch for free on youtube. ocw.mit.edu/courses/mathematics/18-03-differential-equations-spring-2010/video-lectures/lecture-1-the-geometrical-view-of-y-f-x-y/ The textbook can be downloaded for free online, don't buy it. The textbook is also hot garbage imo and I often ended up more confused after reading it than when I started. The TAs are a godsend in this class especially Snyder who was able to condense all of the material into his own lectures in a way more understandable way. The upside is that the tests are very straightforward and often easy or at least easier than the homework. So the class isn't too bad.
Fall 2017 - This class reminded me of high school math classes. The material and workload aren't too bad, but it's really important that you're consistent with all the computations you're making and don't make mistakes. His lectures can be dry and based off the textbook, but I personally found going to lecture worth it. Definitely the most straightforward math class I've taken at UCLA.
Spring 2020 - Allen is the BEST math professor I've had at UCLA. His lectures are super straight forward once you get used to the material, and those combined with the homework is everything you need to do well on his tests. His homework is super helpful but can be a bit tricky doing the problems for the first time. People did super well on his tests this quarter (he also gave us a very extended amount of time) with the average being in the high A range. That being said, I feel like even during a regular quarter his tests would be super reasonable and test you exactly on what he has taught you. Allen is so dedicated and offers a bunch of office hours, and will go so far as to schedule an extra OH on the weekend if he gets a lot of questions. He also responds to your questions super quickly via email or piazza. I would 100% retake this class with him, it has been my favorite math class. Also shout out to Jeremy Brightbill, the best TA with the most life-saving review sessions who will hold office hours until every person has asked every single one of their questions, even if it means logging out of zoom at 11pm.
Goldbring is an unfair and unjust professor who has a binary grading scheme and doesn't curve the class. I missed two negatives and that took me from a B+ to a D- on the first midterm. ON the second midterm i ran out of time but described what i would have done which was correct and i ended up getting a 53 on that test. This guy is a jerk and pretty much reads verbatim from the book and uses those examples too. If you go to office hours he just repeats what he says in lecture and says nothing of use and nothing new. He is not helpful and doesnt care whether you know the material or not just if you come out with the right answer.
Dr. Grossman is rather difficult but it is matched by his willingness to help. I took two courses with him and throughout both quarters he would stay well after office hours to help me (sometimes 3 hours over and this was not an isolated event). The homework questions that he writes are difficult and I almost always had to ask him how to do it but they make you think and you get a good grasp of the material after that. So, he is difficult but take the initiative to ask for help and you will be okay. Good luck.