Meaning of "I have often seen Essex cheese quick enough"

Heywood is rhyming "thick enough" with "quick enough" and at the same time making a pun.

The word "quick" not only relates to speed, but to the state of being alive. We still use it in that sense today in the expression "the quick and the dead", and when we tear a fingernail "down to the quick".

Apparently Essex cheese had a reputation for being infested with worms:

A cantle of Essex cheese
Was well a foot thick
Full of maggots quick.
It was huge and great
And might strong meat
For the devil to eat.
It was tart and punicate.
— John Skelton - Wikipedia

This wasn't necessarily considered a bad thing at the time:

Daniel Defoe in his 1724 work A tour thro' the whole island of Great Britain notes, "We pass'd Stilton, a town famous for cheese, which is call'd our English Parmesan, and is brought to table with the mites, or maggots round it, so thick, that they bring a spoon with them for you to eat the mites with, as you do the cheese." — Stilton cheese - Wikipedia

Note that maggot infested cheese is to this day considered a delicacy in some areas, such as Italy's Casu marzu - Wikipedia:

“Quick” is being used here in the sense of being alive or moving, as in quicksilver, quicksand, or ‘the quick and the dead’.

The Essex cheese could either be a very soft and runny cheese or, as suggested by Ray Butterworth, ‘alive’ with maggots. Not being familiar with Essex cheese, as in I have never heard of it or seen it, it could be either of those but the preceding reference to ‘thick enough’ suggests runny as an opposite to thick.