Why has zuò//láo // in between?
The // is the marker used by Pleco to indicate that the word is in a special class of intransitive verbs called separable verbs.
Other references call these V.O. (Verb Object) constructions. ABC dictionary gives a useful TL;DR summary:

V.O. (Verb-Object Construction, Dòng-Bīn Jiégòu 动宾结构). Many English
verbs get translated into natural Chinese as a verb plus an object
noun, e.g. chīfàn for 'eat', shuōhuà for 'speak', etc. It is important
for two reasons to know what is merely a verb in Chinese and what is
actually a verb-object construction. First, verb-object constructions
can never take a second object, i.e. chīfàn can never be followed
directly by something else to be eaten. Second, a verb and its object
can be separated from one another, thus allowing (i) aspect particles
to be placed directly after the verb, e.g. chīle fàn 'after finishing
eating'; (ii) modification of the object, e.g. chī Zhōngguófàn 'eat
Chinese food'; and (iii) quantification of the noun, e.g. chīle sān
wǎn fàn 'ate three bowls of rice'.

The notion of separable verbs can be a very useful thing to be aware of as a student. This introduction and this list of separable verbs from allsetlearning.com may be helpful references on this topic.