that means ，it is a really very difficute to do somethin, nine bulls & two tigers ,all of them are very strong and powerful,they are emphasized if sb to do sth ,must need work hard , and 九牛二虎 's chinese pronunciation have a good rhyme

It takes you great efforts or energy (as much as nine bulls and two tigers ' ) .. (metaphar used again)

it means "too hard to do sth"! 哈哈，ok？就这么简单！ it is a chinese folk adage.

Fee the off-beat 就是这件事很难 用了 九头牛两只老虎的力气才能完成 it is describe very difficute to do some thing Exaggerating rhetoric it need nine cattles and two tigers power