Let's take a look at the phrase:
<span> Jealousies will be always arising;
insurrections will be constantly happening
both parts have the structure of
noun-plurar WILL BE adverb verb-ING.
So we see that both parts have a similar structure; we call it a parallel structure - the strategy is parallelism, the use of parallel structures to highlight a similarity between two things
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I'd say, since cats are known for being stealthy and sneaky, that Mercutio was calling Tybalt, well, stealthy and sneaky. I think the Prince of Cats thing is also an allusion because I remember reading about it somewhere but I can't remember much (eek! sorry...) <span>
But yeah, I think he was saying that Tybalt is sneaky and stealthy, but also skillful in many ways, and treacherous, to say the least.</span>
