Discussion forums like Piazza can really help with stuff like this. By allowing students to communicate with each other in public, with TAs/instructors explicitly present answering questions, the need to get a group chat going diminishes and you avoid the temptation to cheat.
As an aside, I will say, weekly quizzes are one of the lowest-reward types of homework. They are mainly favored by instructors because they are automatically graded, and they do really little to make you excited about the material. Students recognize and respond to instructor effort (or a lack thereof); if there’s a written assignment every two weeks that students know you are going to take time to grade and give feedback on, then they are significantly more likely to invest the effort to do it well.
As an aside, I will say, weekly quizzes are one of the lowest-reward types of homework. They are mainly favored by instructors because they are automatically graded, and they do really little to make you excited about the material. Students recognize and respond to instructor effort (or a lack thereof); if there’s a written assignment every two weeks that students know you are going to take time to grade and give feedback on, then they are significantly more likely to invest the effort to do it well.