Thanks

come on, man, just type in the problem when it looks like this.
it's a DS problem, so you don't even have to go to the trouble of typing the answer choices.

we have the equation zt < -3, and it wants to know whether z < 4.

(1) alone: If z < 9, then we still don't know whether z < 4. (For instance, z could be 3 [yes] or 5 [no].)
(2) alone: If t < -4, then we know that z is a positive number (because the product is negative and t is negative). you can't really divide two inequalities in any simple way, so just try plugging numbers. let t be, say, -10, and try z's that are greater than 4 and less than 4 (remember, the point here, as on all DS problems, is to prove 'MAYBE'). make sure that you don't violate the condition zt < -3.

if t = -10 and z = 1, then the condition zt < -3 is satisfied, and z is not < 4.
if t = -10 and z = 5, then the condition zt < -3 is satisfied, and z < 4.
these two results show that (2) alone is insufficient.
in fact, the same two results show that statements (1) and (2) TOGETHER are insufficient (since both of the z's selected here happen to be < 9).

answer = e

Is it wrong if I simplify the stem as below?

zt < -3

z < -3/t

and since t < -4 from Statement 2:

if t = -5 --> z < -3/-5 = 0.6 --> z < 0.6 is less than 4

if t = -10 --> z < -3/-10 = 0.3 --> z < 0.3 which is less than 4

yeah, that's wrong.

you can't divide by t unless you've ascertained whether t is positive or negative. and moreover, if t is negative, then you have to switch around the inequality sign ("<" becomes ">").
so if t < -4, then you actually have z > -3/t, not "<".