You should answer the question now that I’ve pointed out Zerg has more production channels to maintain than Terran. Not to mention the fact that Zerg production is much more complex than queuing up marines (swarm host production has a timing & positioning element that is completely absent from all terran production for example).
If your logic was that having more production channels makes it harder to manage your production, then you’re right and that’s why Zerg requires more APM and that’s why Zerg has higher APM across the board for every league in SC2. It’s also the reason why Zerg is the least played race in general, and why low skill players avoid playing it like the plague. They just don’t have the required apm.
The fact that Protoss has roughly twice the number of GMs while having the average APM of masters level zergs is a big problem. Average APM is a VERY good indicator of skill. It means GM is populated with masters level protoss players through a balance boost of something in the ballpark of 500 mmr.