what are skiing, skating and sliding in arabic and their verbs forms ?
Skiing - to ski

skating - (with skateboard or roller-skates) to skate

to slide - ( using the childrens slide at a park)

Question

what are skiing, skating and sliding in  arabic and their verbs forms ?
Skiing  - to ski

skating - (with skateboard or roller-skates)  to skate

to slide - ( using the childrens slide at a park)

Answer

Skiing and skating have the same meaning it is التزلج والتزحلق  , but when  you wanted to say about the specific type of skiings you say like this 
التزلج/التزحلق على الجليد
التزلج/ التزحلق على الرمال
التزلج/التزحلق على الماء
 sliding have a meaning other than التزلج والتزحلق
sliding : انزلاق
  in arabic don't use انزلاق in the expression of sport, but for an accident like that someone slips for stairs
إنزلق زيد  عن الدرج

This site for conjugation  
http://qutrub.arabeyes.org/index
Add the word and clickصرف الفعل  then gives you all the conjugation
if you don't know all the conjugation 
you only see the first column (past) and third (present tense) and sixth ( imperative)

Answer

Ski=التزلج، تزلج بالمزلاج
Skate=التزحلق، تزحلق (يمكن أيضا تزلج) بلوح التزلج
Slide=الانزلاق، انزلق