The Hamilton-Waterloo Problem HWP(v; m, n; α, β) asks for a 2factorization of the complete graph K v or K v − I, the complete graph with the edges of a 1-factor removed, into α C m -factors and β C nfactors, where 3 ≤ m < n. In the case that m and n are both even, the problem has been solved except possibly when 1 ∈ {α, β} or when α and β are both odd, in which case necessarily v ≡ 2 (mod 4). In this paper, we develop a new construction that creates factorizations with larger cycles from existing factorizations under certain conditions. This construction enables us to show that there is a solution to HWP(v; 2m, 2n; α, β) for odd α and β whenever the obvious necessary conditions hold, except possibly if β = 1; β = 3 and gcd(m, n) = 1; α = 1; or v = 2mn/ gcd(m, n). This result almost completely settles the existence problem for even cycles, other than the possible exceptions noted above.