My opinion is that it was very important in the past, when you could sell products in the zoo buildings, but now that they did away with that functionality it really doesn't provide much benefit. The zoo tasks are really long (the 135 points ones), there are no zoo events, it doesn't play at all in the Race of Champions, you don't get any decent amount of coins or XP from filling the orders, half the orders are crazy amounts of difficult and very requested products (like 9 rubbers)... and the materials needed for the last enclosures take up a huge part of your barn... i think it was about 500+ materials for the last enclosure.
The pros of playing it are: TCash for finishing enclosures, TCash from Zoo achievements, Clovers for House of Luck, and i can't think of anything else. Oh, when you are done with the zoo, they stop giving you zoo cards as rewards for events and such, but they mostly replace them with mine tools or bricks and the such.