The major product Z formed in the following sequence of reactions...

Ethane undergoes free radical halogenation with chlorine in the presence of UV light to form ethyl chloride (X).

$\text{C}_2\text{H}_6 + \text{Cl}_2 \xrightarrow{\text{UV light}} \text{C}_2\text{H}_5\text{Cl} \ (X)$

Ethyl chloride reacts with ammonia via nucleophilic substitution to form ethylamine (Y).

$\text{C}_2\text{H}_5\text{Cl} + \text{NH}_3 \rightarrow \text{C}_2\text{H}_5\text{NH}_2 \ (Y)$

Ethylamine, being a primary aliphatic amine, reacts with nitrous acid ($\text{NaNO}_2 + \text{HCl}$) to form an unstable aliphatic diazonium salt, which decomposes to yield a carbocation. The carbocation reacts with water to form ethanol (Z).

$\text{C}_2\text{H}_5\text{NH}_2 \xrightarrow{\text{NaNO}_2/\text{HCl}} [\text{C}_2\text{H}_5\text{N}_2^{+}\text{Cl}^{-}] \xrightarrow{\text{H}_2\text{O}} \text{C}_2\text{H}_5\text{OH} \ (Z) + \text{N}_2 + \text{HCl}$

Thus, the major product Z is $\text{C}_2\text{H}_5\text{OH}$.

Answer: $\text{C}_2\text{H}_5\text{OH}$