In a sense, these are similar because they both involve having the government exert less control over their citizens. Even so, there are differences.
Economic liberalization involves reducing government involvement in the economy. It involves having countries do things like privatizing companies. An example of this from Latin America is when Mexico privatized its airlines instead of having them be owned by the government.
Political liberalization involves reducing how much countries try to control their people. It involves things like more guarantees of people's rights. An example from Mexico might be the increased level of effective voting rights that Mexicans have had since the PRI has stopped being able to steal elections.