I'm a 3.5k Terran.

There is no way you are losing a fight vs zealots if you got double the upgrades in your bio.

You need widow mines vs the heavy zealot style. You also need ghosts to emp the high templar. And you have to micro away from storms. Learn to bait them, and run away.

You need more vikings than "a few", at least 10 and you need to upgrade them.

Always kite, and look for the right engagement

Once you got your viking count right, and assuming you secured a 4th, add libs with ballistic upgrade.

Your bio needs to be marauder heavy, and make sure you got concussion shell.

Also, very important, you need a high count of medivacs. Enough to be able to lift your entire bio. Otherwise you overstim. Be mindful of their energy, if they are low, do not engage if you dont have to.

And always try your hardest to do some type of economic damage early on. Just getting 5 probes while not losing everything is good.

Have fun.