Here's some imaginary videotape of a session with a perfected Zero System and hopefully transparent mechanics. I'll quote what Bill White wrote as a good starting point, with only a few minor changes. I've also included my own best guess as to what a transparent system could use as mechanics. I hope Bill doesn't mind too much.
COL. HEINRICH VON OSCHENKOSCH
Heinrich von Oschenkosch is the scion of an aristocratic Prussian military family who served with great distinction as an aviator during the Great War. Turning to politics after the war, he became an outspoken critic of the Nazi party. His life was threatened several times, and he was assaulted by party thugs, but continued to organize against the Nazis. After his home was firebombed and his family killed in the resulting fire, he left Germany for England, and spent several years there attempting to persuade politicians to take stiff action against Hitler. There he fell afoul of the Star Cult, foiling an attempt on the life of the American ambassador. Eventually, he moved on to the United States. He believes that war with Germany will ultimately break out, and wishes to ensure that America falls in on the side of freedom. He believes that the Nazis will do all they can to weaken America, and seeks to prevent this. Ultimately he hopes to muster a force of “flying volunteers” to take the battle to the Nazis. In the meantime, he lives off his savings and the royalties from his memoirs, cultivating contacts in American business, politics, and the military. His old Great War enemy, Capt. Pierre Ledroit, believes that he was libelled in the Colonel's memoirs, and is waiting for an opportunity to avenge himself against the Prussian aviator, preferably in a duel in the skies.
Amongst Von Oschenkosch's notable possesions is a sword-cane and manouverable biplane.
GM: “You're in your biplane over the English countryside, blanketed in fog. You hear the sound of gigantic motors humming. Looming through the mist in front of you is a giant grinning skull painted on the nose of a swastika-bedecked zeppelin! To your left and right you hear the sound of smaller engines, which you recognize as those of Fokker biplanes. The chop-chop-chop of machine gun fire sounds noisily in your ears. WHAT DO YOU DO?”
Player: “Von Oschenkosch throws his manouverable biplane into a sudden dive and bank to the left, trying to throw off the aim of the firers, and cross their field of fire. He aims to come up on the underneath and going away from the zeppelin, to it's right.”
GM interjects, out of character: “That's a chancy manouever, he might not be able to dodge all those bullets.”
Player replies, out of character: “Von Oschenkosch served with great disctinction in the Great War, and has a manouverable biplane, which should be enough to do it.”
GM states: “let's roll dice to determine the outcome of the shooting, as we don't agree and the situation is risky.”
GM rolls one dice for each of the firer's accuracy, (I assume) two Fokker pilots and one Zeppelin bow gunner, as they are all competent. The dice are rolled by the GM and aren't summed at all.
Player rolls one dice for each applicable descriptor and sums them, which are pilot skill (Von Oschenkosch is competent pilot), experienced (he survived the Great War!), distinction and great distinction, and manouverable biplane; a total of five dice to roll and sum as all the descriptors aid each other.
It's highly likely that the player's 5D6 dice roll total will be higher than any of the opposition dice, so the Colonel manages to dodge the MG fire.
GM: “The bullets miss, but two of the Fokkers pull around and follow, coordinating their fire on your biplane.”
Player: “Von Oschenkosch weaves his biplane in a corkscrew, slowing and allowing the two Fokkers to overshoot him. The Zeppelin gunners aren't firing as they risk hitting their fighters.”
GM and player again agree to roll dice as the situation is risky. GM rolls 2 dice and sums them as the two Fokker pilots are coordinating their fire; and informs the player that he must drop one dice as he's doing one more action than the Fokker pilots are. Player rolls 4D6 (5D6 - 1D6 for two actions). Again, it's quite likely that the Player's roll of 4D6 is higher than the GM's roll of 2D6.
GM: “The fokkers miss again, their bullets flying no where near you. You're now behind the two Fokkers, though both pilots are desperately trying to slow their 'planes to get behind you.”
Player: “I use my manouverable biplane and skill to maintain my position, and trigger a long burst into the right Fokker.”
GM and Player agree that the Fokker's are average biplanes, and that the Colonel's manouverable biplane has the edge in going slower than an average biplane. GM rules one contest for position and then a second contest for the shooting. GM rolls one dice for each Fokker pilot, and Player divides 5D6 into 2D6 against the left Fokker and 3D6 for the right Fokker. (I'll assume that the player's roll wins versus the right Fokker and looses to the Left Fokker.)
GM: “The left Fokker manages to get on your tail as you concentrate on the right Fokker, as he desparately tries to dodge your attack.”