WASHINGTON, Aug. 24— Zbigniew Brzezinski is willing to give everyone a fighting chance. At least on the tennis court.

The former White House national security adviser – better known on the Washington scene for confrontation than conciliation – is a passionate tennis player. With the cooperation of Kathy Kemper, a local tennis coach, he has devised a scoring system that he says helps equalize the game when mismatched players face each other.

”In the conventional handicap system, the inferior players will often have too great or too small a handicap,” Mr. Brezinski said in a recent article he wrote about what he calls the ZBalanced Handicap System. ”This makes for a dull match. Also, with the handicap fixed, there is no allowance or even psychological incentive for the inferior player to play with growing confidence.”

”It’s the Brzezinski mind behind this,” said Miss Kemper, who has the decided edge on the court over Mr. Brzezinski. ”When we play his handicap system, it puts the pressure on me and makes it more fun. Normally if you win the first two games, you feel fairly confident. But with his handicap system I can only afford to lose one point in the third game and I can’t screw around.”

In tennis, points are scored: 15, 30, 40 and game. The first person to win six games wins the set. Handicap Can Shift

In the Brzezinski system, the first game is scored normally. If the weaker player loses the first game, he has only to reach 40 to win the second game. If he still loses the second game, he must reach only 30 to win the third game. Even if the stronger player is leading 40-15, for example, the game is won by the weaker player if he gets the next point, reaching 30.

Assume the weaker player wins the third game; in the next game his handicap will be toughened by one step and he must reach 40 to win. The handicap can shift up or down one notch depending upon the outcome of each game. It can reach the point where the inferior player may only need to win one scoring point (15) to win.

If the better player wins the first set, the next set begins with the handicap determined by the last winning game of the first set.

”I’ve used this system against much better players than I, and I’ve found it makes for a genuine match,” said Mr. Brzezinski, whose hallmark on the court is tenacity rather than finesse. ”It’s fun to see how even the best and most confident player begins to tighten up if he or she has to win a game at love.”

”There is nothing,” he added, ”like devastating your opponent with a good, clean shot with precision and power.”