Two electrons are moving with the same speed $v$. One electron enters a region of uniform electric field while the other enters a region of uniform magnetic field. After sometime if the de-Broglie wavelength the two are ${\lambda }_1$ and ${\lambda }_2$, then

Speed of first electron may increase or decrease, depending on the direction of electric field. However in the case of electron entering the magnetic field speed remains constant as the force due to field is always perpendicular to the velocity. 

Since, from de-Broglie relation

$$\begin{gathered} \lambda =\frac{h}{mv} \text{,} \\ \Rightarrow {\lambda }_1>{\lambda }_2 \text{or } {\lambda }_2>{\lambda }_1 \end{gathered}$$

are both possible.