This translation makes perfect sense, so we are looking at the kind of game described by Huck.Ross G. R. Caldwell wrote:For "zurlo" the Zingarelli says "a variant of ciurlo, attested by 1449". They say it means "Ruzzo" (Tuscan).
Ruzzo seems to mean "whim, fancy, or caprice".
Ciurlare means to sway or totter -
It seems to refer to the behavior of the "ball" (looks like a cheese roll here), which would roll or totter one way or the other in a capricious fashion.
So maybe "Be careful of the (roll of the) Zurlo, that it doesn't knock down the Matto, because then the turn is null."
Edited to add -
Ottavia Niccoli, in "People and Prophecy in Renaissance Italy", without going into the etymology of zurlo, translates it as (p. 26) -
"Take care that the zurlo does not strike down the Mato, because if it does the match is off."
Interestingly, the "ball" is not a ball.
This reminds me of the "Game of the sphere" (De Ludo Globi) by Nicolaus Cusanus:
http://books.google.com/books?hl=it&id= ... id&f=false
Also in that case, the game was based on a "ball" with an irregular shape. And also in that case the strange movements of the ball were interpreted as a metaphor of the world.
Such wild movements will certainly require some "fortune" in order to win the game. I think that the image intentionally recalls a wheel of fortune, as proposed by Robert.
The cities that are still standing with Venice could be:
Vicenza, Padova, Treviso.
The trees can indeed refer to the Pope, France and Spain, as suggested by Huck. But what is the meaning of the banners?