A mod called CrackedZombie will allow zombies to appear in the game world even during the day. Now you can’t relax because zombies will always haunt you.
CrackedZombie Mod for Minecraft 1.15.1/1.15/1.14.4
Nevertheless, this way you can get more experience and drop from mobs. So the mod is pretty cool overall.
1.15.1/1.15 – cezombiemod_1.15.1_1.2.0_9
1.14.4 – cezombiemod_1.14.4_1.1.0_5