Ox and Horse compatibility
Ox (Chou, 丑) and Horse (Wu, 午): a harm (Hai, 害).
These are fixed relations among the twelve branches of the Chinese calendar, set out in the classic San Ming Tong Hui (三命通会), written in 1578, quoted below. They describe the signs, not two people: no classic gives a method for matching two people by their signs, so there is no score here.
What the book says
Harm (Hai, 害)
Why it is called harm: one befriends the other’s opponent. The Ox clashes with the Goat, and the Horse is in a six harmony with the Goat.
The six harms are where the twelve branches override and fight one another.
六害者，十二支凌战之辰也。
Ox and Horse harm each other because the Horse, Fire at its height, overrides the Ox, where Metal lies dead. It is called the harm of officer and ghost.
丑午相害者，谓午以旺火凌丑死金，名官鬼相害。
The Ox fears the Goat’s clash, and the Horse goes off and joins the Goat.
丑畏未冲，而午却去合未
Six: the six kinds of kin. Harm: loss. Having it means loss and friction among one’s closest family; hence the six harms.
六，六亲；害，损也。犯之主六亲上有损克，故谓六害。
San Ming Tong Hui, volume 2: On the six harms (论六害) · source text
Their elements
The Ox is Earth and the Horse is Fire: Fire feeds Earth.
How much it counts
A sign is one character of the eight in a BaZi chart, the year’s branch. The book reads these relations between the pillars of one chart, and tells the reader to look at the whole chart’s elements first:
Clash and break, three harmony and six harmony: where a chart has them, ask next how its five elements get on. Misfortune may give rise to blessing, and blessing to misfortune.
相冲相破，三合六合，命中有之，即求五行相得何如。或祸中生福，福中生祸
San Ming Tong Hui, volume 3: On the symbolic stars as a whole (总论诸神煞) · source text
Birth years, and 2027
- Ox: 1925, 1937, 1949, 1961, 1973, 1985, 1997, 2009, 2021. In 2027, the Year of the Fire Goat (Ding Wei, 丁未), the Ox clashes with the year (Chong Tai Sui, 冲太岁) and is punished by the year (Xing Tai Sui, 刑太岁).
- Horse: 1930, 1942, 1954, 1966, 1978, 1990, 2002, 2014, 2026. In 2027, the Year of the Fire Goat (Ding Wei, 丁未), the Horse is in harmony with the year (Liu He, 六合).
A sign’s year is usually counted from Chinese New Year, between late January and mid-February; BaZi counts it from the Start of Spring, about 4 February. Born in January or early February? You may be the sign before: the sign pages check your date.
Two real people?
Each person’s chart has eight characters, and the same relations run between all of them, not only the two signs. The two-chart page sets both charts side by side, branch by branch, and gives what each chart says about marriage on its own. No score there either.
Ox with the other signs: Rat · Ox · Tiger · Rabbit · Dragon · Snake · Goat · Monkey · Rooster · Dog · Pig.
Horse with the other signs: Rat · Tiger · Rabbit · Dragon · Snake · Horse · Goat · Monkey · Rooster · Dog · Pig.