I stock 48V battery but where did you get your TSDZ2? You need a battery that can support 150% maximum current drain.
For example, a 48V 12AH can support up to 1.5C maximum, that is 48V 18A, good enough for 500W continuous but not 750W.
The 750 watt draws 15 amps how deep are you pockets and how much weight do yo want to add
my personal opinion is no cheap Chinese cells get a branded cell Samsung or Sanyo ga cells the pack needs to be around 17 ah at 48v the tsdz2 will not run 52v packs without modification try not cheapest but good uk service https://ebikebatteries.co.uk/product-category/ebike-battery-pack/tiger-shark/48v/