Any Operating System, if bottlenecked, will run slower.
We speak of Zorin because this is the Zorin Forum. If this was the Manjaro forum, I would have said that it would make Manjaro run slower.
A partition is a block of your hard drive assigned to a specific task or Operating system. A partition is separate from another partition.
Let's say that you divide a 1 terabyte partition into two equal halves making two partitions of ~500gigs each. It would be basically the same as having two 500gig HDD's, instead of one 1ter HDD.
Given the speed records Zorin 16 appears to be shattering in The Road To Zorin 16, I wouldn't bank on it.