That depends on whether the new employer has an agreement with EK not to poach each other’s cabin crews.
It’s not EK that will actively prevent employment, it’s the new prospective employer that may withdraw the offer if they should have such a reciprocal agreement.
In case of the new employer being in the same scountry (e.g. UAE), you also need to consider that EK will cancel your residence visa when you leave, which may prevent you from getting a residence visa in the UAE.
Only certain categories of employees (usually with higher qualifications) can change employment in the UAE without the consent of the previous employer.
B.