(Not fair because it is in the training set, but o3-mini-high gives a thorough answer after 66s)

Below is a step‐by‐step reasoning that leads to the well‐known solution of the “Zebra Puzzle.”

Step 1. Number the Houses 1 to 5

We assume the houses are arranged in a row from left to right, with House 1 on the far left and House 5 on the far right.

Step 2. Assign the Easy Clues
1. H10: “The Norwegian lives in the first house.”
→ House 1: Nationality = Norwegian.
2. H15: “The Norwegian lives next to the blue house.”
House 1 has only one neighbor (House 2), so
→ House 2: Color = Blue.
3. H09: “Milk is drunk in the middle house.”
→ House 3: Beverage = Milk.

Step 3. Determine the House Colors with the Ivory/Green Pair
• H06: “The green house is immediately to the right of the ivory house.”
There are two possible placements for this pair: either Houses (3,4) or Houses (4,5).
The option (3,4) would force House 3 to be ivory, but later clues will assign House 3 a color (red, see H02) for the Englishman.
So we take the pair as Houses 4 and 5:
• House 4: Color = Ivory.
• House 5: Color = Green.
• H04: “Coffee is drunk in the green house.”
→ House 5: Beverage = Coffee.
• The remaining colors for Houses 1–3 are now Red, Yellow, and (already used) Blue.
H02: “The Englishman lives in the red house.”
Since House 1 is taken by the Norwegian and House 2 is blue, the only possibility is:
→ House 3: Color = Red, Nationality = Englishman.
• The only color left for House 1 is Yellow.
H08: “Kools are smoked in the yellow house.”
→ House 1: Color = Yellow, Cigarette = Kools.

Step 4. Assign the Remaining Nationalities and Beverages

The nationalities so far:
• House 1: Norwegian
• House 3: Englishman

Remaining nationalities: Ukrainian, Spaniard, Japanese.
• H05: “The Ukrainian drinks tea.”
House 2 already is blue and unassigned for nationality and beverage, so:
→ House 2: Nationality = Ukrainian, Beverage = Tea.

Now for Houses 4 and 5, the remaining nationalities are Spaniard and Japanese.
• H03: “The Spaniard owns the dog.”
And
• H14: “The Japanese smokes Parliaments.”

We still have the beverages and cigarettes to assign. Notice that House 5 (green) already has its beverage (coffee). It is natural then to assign:
• House 5: Nationality = Japanese, Cigarette = Parliaments.
This leaves:
• House 4: Nationality = Spaniard, and by H03,
→ House 4: Pet = Dog.

Step 5. Use the Clues about Cigarettes and Pets

The remaining cigarette brands to assign (across Houses 2, 3, and 4) are: Old Gold, Chesterfields, and Lucky Strike.
• H13: “The Lucky Strike smoker drinks orange juice.”
House 5 already drinks coffee; House 3 has milk; House 2 has tea; so the only house with an unassigned beverage is House 4.
→ House 4: Beverage = Orange juice, Cigarette = Lucky Strike.
• Now, the remaining cigarettes for Houses 2 and 3 are: Old Gold and Chesterfields.
• H07: “The Old Gold smoker owns snails.”
• H11: “The man who smokes Chesterfields lives in the house next to the man with the fox.”
• H12: “Kools are smoked in a house next to the house where the horse is kept.”
House 1 (which smokes Kools) has only one neighbor, House 2, so:
→ House 2: Pet = Horse.

Now, consider Houses 2 and 3 for the remaining cigarette assignments:
• If House 2 were the Old Gold smoker, then by H07 it would have to own snails—but it already has the horse.
So, House 2 must smoke Chesterfields, and consequently,
→ House 2: Cigarette = Chesterfields.
• This forces:
→ House 3: Cigarette = Old Gold, and by H07,
→ House 3: Pet = Snails.

Finally, H11: “The man who smokes Chesterfields lives in the house next to the man with the fox.”
House 2 (smoking Chesterfields) is adjacent to Houses 1 and 3.
House 3 already has snails, so
→ House 1: must have the fox.
→ House 1: Pet = Fox.

The only pet left is the zebra. The only house without a pet now is House 5, so:
→ House 5: Pet = Zebra.

Step 6. Assign the Final Beverage

At this point, the beverages are:
• House 2: Tea
• House 3: Milk
• House 5: Coffee
• House 4: Orange juice

The only beverage not yet used is water. The only house still without a beverage is House 1, so:
→ House 1: Beverage = Water.

Final House Assignments
• House 1:
Color: Yellow
Nationality: Norwegian
Beverage: Water
Cigarette: Kools
Pet: Fox
• House 2:
Color: Blue
Nationality: Ukrainian
Beverage: Tea
Cigarette: Chesterfields
Pet: Horse
• House 3:
Color: Red
Nationality: Englishman
Beverage: Milk
Cigarette: Old Gold
Pet: Snails
• House 4:
Color: Ivory
Nationality: Spaniard
Beverage: Orange juice
Cigarette: Lucky Strike
Pet: Dog
• House 5:
Color: Green
Nationality: Japanese
Beverage: Coffee
Cigarette: Parliaments
Pet: Zebra

Cross Check Against the Clues
• H02: Englishman in the red house → House 3 is red and English.
• H03: Spaniard owns the dog → House 4 (Spaniard) has a dog.
• H04: Coffee in the green house → House 5 (green) has coffee.
• H05: Ukrainian drinks tea → House 2 (Ukrainian) has tea.
• H06: Green house is immediately right of the ivory house → Houses 4 (ivory) and 5 (green).
• H07: Old Gold smoker owns snails → House 3 (Old Gold) has snails.
• H08: Kools in the yellow house → House 1 (yellow) smokes Kools.
• H09: Milk in the middle house → House 3 has milk.
• H10: Norwegian in House 1 → correct.
• H11: Chesterfields smoker (House 2) lives next to fox owner (House 1).
• H12: Kools (House 1) next to horse (House 2).
• H13: Lucky Strike smoker (House 4) drinks orange juice.
• H14: Japanese smokes Parliaments → House 5.
• H15: Norwegian (House 1) lives next to blue house (House 2).

All clues are satisfied.

Final Answers
• Q1: Who drinks water?
→ The Norwegian in House 1 drinks water.
• Q2: Who owns the zebra?
→ The Japanese in House 5 owns the zebra.

Sources and Further Reading
• For a classic discussion of this puzzle and its variations, see “Einstein’s Riddle” as presented in various logic puzzle collections and articles such as those found on Brainzilla or in books on lateral thinking puzzles.

This structured reasoning confirms the answers with a high degree of certainty.