We can Install Android marshmallow 6.0 in motorola Moto E 2nd gen by flashing Cm13 in it.As this is Unofficial Cm13 rom for Moto E 2nd gen so there may be bugs in it you change check the source thread for XDA for the bugs and stability report.
We already shared the guide of installing CM13 on Motorola Moto G 2nd gen and CM 13 for Moto G 1st gen and CM 13 for Moto E 1st gen earlier
you can check it out also now only few device left which are going to
get CM13 soon that are Moto E,Moto G 3rd gen,Moto X play and moto X
Style/pure etc.So follow below guide of Install unofficial Cyanogenmod
13 Rom in Moto E 2nd gen 2015 [otus] only 3g model don’t flash it in 4g model.
2.Custom recovery on your device must be installed like TWRP or CWM.
3.Make back up of Current rom from recovery.
4.Note before flashing rom do check the stability report of CM 13 from HERE.
#How to Install Cyanogenmod 13 on Moto E 2nd gen [OTUS]
CM 13 Rom fro moto e2 2nd gen 2015 3g model only and the appropriate Gapps 6.0 package
from link given below Copy it in your in your device.
2.Now place the Cyanogenmod 13 rom and gapps 6.0 zip file in sd card.
3.Now reboot to Recovery mode and flash Android marshmallow rom in your device.
4.Then flash CM13 android marshmallow rom and gapps from recovery in it.
5.Now Clear cache and Clear Data.
6.Reboot your device.Done! you just flash cyanogenmod 13 rom in your Motorola Moto e2 2nd gen 2015.Enjoy Android Marshmallow 6.0.