$\left ( {1} \right )175\div 5=35\left ( {个} \right )$
$252\div 7=36\left ( {个} \right )$
$36-35=1\left ( {个} \right )$
$\left ( {2} \right )355\div \left ( {35+36} \right )$
$=355\div 71$
$=5\left ( {小时} \right )$
答：$\left ( {1} \right )$张师傅比李师傅每小时少做$1$个零件；
$\left ( {2} \right )$需要$5$小时.
