should i buy toh, or sin's rebirth is better?

i wanna kill izaro before he will start moving, at the moment i ve got atziri+lion's roar. totems build.
-as i understand if i use toh and take any phys dmg, there is a chance that ill be chilled or even frozen? so ill ned anti-chill flask?
-does aziri and toh will work if i use them at the same time? or i will loose bonus dmg from flask that was used first? (like can there be 3 dmg source for me? chaos dmg from atziri, cold from toh and physical dmg?)
p.s. both flasks need for dmg, not for defences.

Assuming I've translated your post properly...

First of all: Taste of Hate gives you a chance to avoid being Chilled or Frozen; it doesn't add that chance to you. With Taste of Hate active, any time you would otherwise become Chilled or Frozen, the flask effect rolls a die to see if you instead don't become Chilled/Frozen.

Second of all: Any flask effect that is not a duplicate of an existing flask effect is retained. I.e. you can activate Lion's Roar to gain 3000 armor because Lion's Roar isd a Granite flask, as well as gaining Knockback and also a bunch of melee physical damage. Then you can activate Rumi's Concoction, which grants you extra block chance and spell block chance. With both of these flasks active, you will have Knockback, Melee damage, Block chance, and Spell Block chance, but you only get 3000 armor froma ctivating a Granite flask once, even though both Rumi's Concoction and Lion's Roar are Granite flasks.

Short answer: yes. Atziri's Promise and Taste of Hate stack.

Third of all: choice between Taste of Hate and Sin's Rebirth is entirely build dependent. Do you have a lot of ways to scale up elemental damage in your build? Do you have a lot of ways to scale up Chaos damage, instead? Do you already have a source of Unholy Might? Sin's Rebirth is a bigger conversion (30% from Unholy Might, as opposed to 20% for a max-rolled Taste), but Chaos damage doesn't have as many ways to scale as Elemental damage does, and also Unholy Might doesn't stack with itself. Sin's Rebirth is useless if you have another source of Unholy Might, and if your build uses stuff like Elemental Damage with Attacks or Elemental Focus supports for your main skill, Taste is probably worth more overall DPS anyways.

Pick whichever one works best with your primary skill and go.