zu and ji...

Im trying to learn hiragana and katakana. Im studying hiragana right now. im just wondering. Why is the zう, zu, ji, ji

there are 2 of each. In hiragana and katakana they have 2 different symbol character thingys. but what is the difference?

one is with: za JI ZU ze zo
the other is with: da JI ZU de do

whats the difference?☝

The ones used in the ta column are only used in special circumstances tuduku, chijimu etc. The ones in the sa column are usualy used to represent these sounds and are not uncommon.

「トミイ」は「トミー」に That line is used to make long vowels in katakana.
mojibake there so i can't read it, but にほんご が すこし はなせます works.