Zen is not a brand. It's a codename for the evolution of their CPU architecture.
Zen, Zen+, Zen 2 and Zen 3 are the generations of CPU architecture.
Ryzen is the consumer brand of CPUs. Geared towards anyone who doesn't specifically need Threadripper.
Threadripper is the enthusiast/workstation brand of (rather) high core count CPUs. If you run software that uses a lot of cores, you should know whether this is the right line of CPUs for you.
