Introduced new fish with my other fish, i think they're fighting?

[CannedUs]

I had 4 neon tetras, 3 of them passed away and then i just had one, i had him for a few weeks and he seemed happy, but i figured i would get some new fish to keep him company since he is in a really big tank. I got 3 zebrafish and one fantailed guppy. My fish was trying to school with the zebras but they kept chasing him, but they were also chasing eachother so i figured it was fine. Then my guppy was chasing him too. Now my poor little neon tetra keeps hiding in the center plant and only comes out when there is food.

What should i do?
Would getting another neon tetra help him to school or be more comfortable with his own kind?
Helpp
kk yeah i had another guppy but he died today :/
yeah i have two small zebras and one largeish zebra compared to the others and he keeps chasing the smaller zebras??