Jules becomes Darrell Clarke's fourteenth signing of the summer and the third of the afternoon after the gaffer reentered the market following George Dobson's move to Sunderland.
Zak began his career at Reading, rising through the ranks to turn professional in 2015. Despite earning pro terms, Zak failed to make a first-team appearance for the Royals but did enjoy loan spells with Hemel Hempstead Town, Braintree Town, and Motherwell.
Jules penned a two-year deal with Shrewsbury Town in June 2017 but failed to make a single first-team appearance for the Montgomery Waters Meadow side, although he did earn some football with loan sells at Chesterfield, Port Vale, and Barnet.
Islington-born Jules' Shrews nightmare came to an end in January as he agreed to join Sol Campbell's Macclesfield, and went on to play a key role in the Silkmen's successful survival fight in League Two.
Jules' consistent performances are said to have alerted a number of Championship and League One clubs, but the Saddlers have moved quickly to agree a deal to sign the Scotland Under-21 international.
Walsall boss Darrell Clarke spoke to club journalists and welcomed Zak to the club, he said; "He did very well at the back end of last season and is a young player we want to develop.
"He’s a left-sided centre-half, pacey, quick, mobile. I’m really pleased to bring him in and I think we’ve got the balance now.
"It’s just one more centre forward I need now; that will give me a healthy squad that is flexible within formations and has a good mix of experience and ages."
Walsall boss Darrell Clarke spoke to club journalists and welcomed Zak to the club, he said; "He did very well at the back end of last season and is a young player we want to develop.
"He’s a left-sided centre-half, pacey, quick, mobile. I’m really pleased to bring him in and I think we’ve got the balance now.
"It’s just one more centre forward I need now; that will give me a healthy squad that is flexible within formations and has a good mix of experience and ages."