i think i know but it might not work ! ok so get a zip zap u dont realy like and do this
put two wires or whatever the thing conecting the 1st moter
and tape it over the moter and gear to give it more power or
ummmm
or tape it under the moter on the axel and i think that will work
or under the 1st moter just cut the plastic part and well to show u quickly
G= gear and _ is the plastic and M = so just see
G
M
_ < right there cut that and put the moter i think that might work put u might need a nother moter controler < i spelled that wrong